Pneumonia
Highlights
Diagnosis:
Diagnosing pneumonia may be difficult, since lab tests to grow the bacteria from samples can take many days to process, and chest x-rays cannot always distinguish between pneumonia and other conditions. New tests have the potential to make diagnosis easier and quicker. One is a blood test that identifies a marker of severe inflammation in the body. A new 15-minute urine test shows promise in identifying Legionella pneumophila and Streptococcus pneumoniae in patients on ventilators. Physicians may now sample fluid from the trachea or lungs to identify the pneumonia-causing bacteria.
Treatment:
Treating pneumonia has become increasingly complex as bacteria develop resistance to widely used antibiotics. New antibiotics and combinations of older antibiotics are proving effective against many hardy strains of bacteria. Moreover, guidelines for the appropriate treatment of patients at high risk for pneumonia -- those with heart disease, diabetes, asthma, HIV infection, leukemia, and other lung diseases, for example -- are improving the ability to prevent pneumonia and reduce deaths from the disease.
Drug Warning:
In February 2007, the Food and Drug Administration (FDA) announced that the antibiotic telithromycin (Ketek) would no longer be approved for acute bacterial sinusitis and acute bacterial exacerbations of chronic bronchitis, but it would remain on the market for the treatment of mild-to-moderate pneumonia acquired outside of hospitals or long-term care facilities (community-acquired pneumonia, or CAP). In addition to warnings for liver damage, Ketek will now carry warnings of additional drug-related adverse events, including visual disturbances and loss of consciousness.
Introduction
Pneumonia is an inflammation of the lung that is most often caused by infection with bacteria, viruses, or other organisms. Occasionally, inhaled chemicals that irritate the lungs can cause pneumonia. Healthy people can usually fight off pneumonia infections. However, people who are sick, including those who are recovering from the flu (influenza) or an upper respiratory illness, have weakened immune systems that make it easier for bacteria to grow in their lungs.
When air is inhaled through the nose or mouth, it travels down the trachea to the bronchus, where it first enters the lung. From the bronchus, air goes through the bronchi, into the even smaller bronchioles and lastly into the alveoli.
Defining Pneumonia by Location in the Lung
Pneumonia may be defined according to its location in the lung:
- Lobar pneumonia occurs in one part, or lobe, of the lung.
- Bronchopneumonia tends to be scattered throughout the lung.
Defining Pneumonia by Origin of Infection
Doctors often classify pneumonia based on where the disease is contracted. This helps predict which organisms are most likely responsible for the illness and, therefore, which treatment is most likely to be effective.
Community-Acquired Pneumonia (CAP). People with this type of pneumonia contracted the infection outside a hospital setting. It is one of the most common infectious diseases. It often follows a viral respiratory infection, such as the flu.
One of the most common causes of bacterial CAP is Streptococcus pneumoniae. Other causes include Haemophilus influenzae, mycoplasma, and Chlamydia.
Hospital-Acquired Pneumonia. Hospital-acquired pneumonia is an infection of the lungs contracted during a hospital stay. This type of pneumonia tends to be more serious, because hospital patients already have weakened defense mechanisms, and the infecting organisms are usually more dangerous than those encountered in the community. Hospital patients are particularly vulnerable to Gram-negative bacteria and staphylococci. Hospital-acquired pneumonia is also called nosocomial pneumonia.
A subgroup of hospital-acquired pneumonia is ventilator-associated pneumonia (VAP), a highly lethal form contracted by patients on ventilators in hospitals and long-term nursing facilities.
Click the icon to see an image of hospital-acquired pneumonia.
Disease Process Leading to Pneumonia
Pneumonia-causing agents reach the lungs through different routes:
- In most cases, a person breathes in the infectious organism, which then travels through the airways to the lungs.
- Sometimes, the normally harmless bacteria in the mouth, or on items placed in the mouth, can enter the lungs. This usually happens if the body's "gag reflex," an extreme throat contraction that keeps substances out of the lungs, is not working properly.
- Infections can spread through the bloodstream from other organs to the lungs.
However, in normal situations, the airways protect the lungs from substances that can cause infection.
- The nose filters out large particles.
- If smaller particles pass through, sensors along the airway prompt a cough or sneeze. This forces many particles back out of the body.
- Tiny particles that reach the small tubes in the lungs (bronchioles) are trapped in a thick, sticky substance called mucus. The mucus and particles are pushed up and out of the lungs by tiny hair-like cells called cilia, which beat like a drum. This action is called the "mucociliary escalator."
Click the icon to see an image of respiratory cilia.
- If bacteria or other infectious organisms manage to avoid the airway's defenses, the body's immune system attacks them. Large white blood cells called macrophages destroy the foreign particles.
Click the icon to see an image of a macrophage.
The above-mentioned defense systems normally keep the lung healthy. If these defenses are weakened or damaged, however, bacteria, viruses, fungi, and parasites can easily infect the lung, producing pneumonia.
The Lungs
The lungs are two spongy organs in the chest surrounded by a thin, moist membrane called the pleura. Each lung is composed of smooth, shiny lobes; the right lung has three lobes and the left has two. Approximately 90% of the lung is filled with air. Only 10% is solid tissue. There are several parts to each lung.
When a person takes a breath (inhales), air travels from the trachea (windpipe) into the lung through the main bronchus, which branches into tiny flexible tubes called bronchi.
The bronchi divide, like the branches of a tree, into smaller airways called bronchioles.
The bronchioles lead to a group of microscopic sacs called alveoli, which look like clusters of grapes. Each healthy adult lung contains millions of tiny alveoli. (Note: The singular of alveoli is alveolus.)
Click the icon to see an image of the lungs.
Each alveolus has a thin membrane that allows oxygen and carbon dioxide to pass in and out of the capillaries, the smallest of the blood vessels. When you take a deep breath, the membrane unfolds and expands. Fresh oxygen moves into the capillaries, and carbon dioxide passes from the capillaries into the bloodstream, where it is carried out of the body through the lungs.
Blood vessels carry the oxygen-rich blood to the heart, where it is pumped throughout the body.
Causes
Bacteria are the most common cause of pneumonia. However, pneumonia can also be caused by viruses, fungi, and other agents. It is often impossible to identify the specific culprit.
Many bacteria are grouped into one of two large categories by the laboratory procedure used to look at them under a microscope. The procedure is known as Gram staining. Bacteria are stained with special dyes, then washed in a special solution. The color of the bacteria after washing determines whether they are Gram-negative or Gram-positive. Knowing which group the bacteria belong to helps determine the severity of the disease, and how to treat it. Different bacteria are treated with different drugs.
Gram-Positive Bacteria. These bacteria appear blue on the stain and are the most common organisms that cause pneumonia. They include:
- Streptococcus (S.) pneumoniae (also called pneumococcus), the most common cause of pneumonia. This Gram-positive bacterium causes 20 - 60% of all community-acquired bacterial pneumonia (CAP) in adults. Studies also suggest it causes 13 - 38% of CAP in children.
- Staphylococcus (S.) aureus, the other major Gram-positive bacterium responsible for pneumonia, causes about 2% of CAP and 10 - 15% of hospital-acquired pneumonias. It is the organism most often associated with viral influenza, and can develop about five days after the onset of flu symptoms. Pneumonia from S. aureus most often occurs in people with weakened immune systems, very young children, hospitalized patients, and drug abusers who use needles. It is uncommon in healthy adults.
- Streptococcus pyogenes or Group A streptococcus.
Gram-Negative Bacteria. These bacteria stain pink. Gram-negative bacteria commonly cause infections in hospitalized or nursing home patients, children with cystic fibrosis, and people with chronic lung conditions.
- Haemophilus (H.) influenzae is the second most common organism causing community acquired pneumonia, accounting for 3 - 10% of all cases. It generally occurs in patients with chronic lung disease, older people, and alcoholics.
- Klebsiella (K.) pneumoniae may be responsible for pneumonia in alcoholics and other people who are physically debilitated. It is also associated with recent use of potent antibiotics.
- Pseudomonas (P.) aeruginosa is a major cause of hospital-acquired pneumonia (nosocomial pneumonia). It is a common cause of pneumonia in patients with chronic or severe lung disease.
- Moraxella (M.) catarrhalis is found in everyone's nose and mouth. Experts have identified this bacterium as an uncommon cause of certain pneumonias, particularly in people with lung problems such as asthma or emphysema.
- Neisseria (N.) meningitidis is one of the most common causes of meningitis (central nervous system infection), but the organism has been reported in pneumonia, particularly in epidemics of military recruits.
- Other Gram-negative bacteria that cause pneumonia include E. coli, proteus (found in damaged lung tissue), enterobacter and acetinobacter.
Atypical Pneumonia
Atypical pneumonias produce mild symptoms and a dry cough. Organisms that cause atypical pneumonias include:
- Mycoplasma (M.) pneumoniae, the most common atypical pneumonia organism. Mycoplasma is a very small bacterium that lacks a cell wall. Pneumonia caused by M. pneumoniae spreads when someone carrying the infection comes in close contact with others for a long period of time. It is most often found in school-aged children and young adults. The condition, commonly called "walking pneumonia," is usually mild.
- Chlamydia (C.) pneumoniae is now thought to cause 10% of all CAP cases. This atypical pneumonia is most common in young adults and children, and is usually mild. It is less common, but usually more severe, in the elderly.
- Legionella pneumophila causes Legionnaire disease. It is contracted by breathing in drops of contaminated water. Outbreaks are often been reported in hotels, cruise ships, and office buildings, where people are exposed to contaminated droplets from cooling towers and evaporative condensers. They have also been reported in people who have been near whirlpools and saunas. Legionella pneumophila is not passed from person to person. Some experts believe the organism causes 29 - 47% of all pneumonia cases.
Viral Pneumonia
A number of viruses can cause pneumonia either directly or indirectly. They include:
- Influenza (Flu). Pneumonia is a major complication of the flu and can be very serious. It can develop about 5 days after flu symptoms start. The flu weakens the body's defense systems, making it easier for bacteria to grow in the lungs.
- Respiratory syncytial virus (RSV). Most infants are infected with RSV at some point, but it is most often mild. However, RSV is a major cause of pneumonia in infants as well as adults with damaged immune systems. Studies indicate that RSV pneumonia may be more common in adults, especially the elderly, than previously thought.
- Severe acute respiratory syndrome (SARS). SARS is a respiratory infection caused by a newly-described coronavirus, which appears to have jumped from animals to humans. The disease was first reported in China in 2003.
- Human parainfluenza virus. This virus is a leading cause of pneumonia and bronchitis in children, the elderly, and patients with damaged immune systems.
- Adenoviruses. Adenoviruses are common and usually are not problematic, although they have been linked to about 10% of childhood pneumonia.
- Herpesviruses. In adults, herpes simplex virus and varicella zoster (the cause of chickenpox) can cause pneumonia in people with impaired immune systems.
- Avian influenza. Type A influenza subtype H5N1 in birds is spreading around the globe. Fortunately, only a few hundred human cases have been identified. Most have resulted from close contact with infected birds. Person-to-person contact is rare. All patients diagnosed with "bird flu" show signs of pneumonia, although symptoms may be mild. Oseltamivir (Tamiflu) is the most effective treatment for this type of influenza, which can be fatal.
Aspiration Pneumonia and Anaerobic Bacteria
The mouth contains a mixture of bacteria that is normally harmless. However, if this mixture reaches the lungs, it can cause a serious condition called aspiration pneumonia. This may happen after head a injury or general anesthesia, or when a patient takes drugs or alcohol. In such cases, the gag reflex doesn't work as well as it should, so bacteria can enter the airways. Unlike other organisms that are inhaled, bacteria that cause aspiration pneumonia do not need oxygen to live. These bacteria are called anaerobic bacteria.
Opportunistic Pneumonia
Impaired immunity leaves patients vulnerable to serious, life-threatening pneumonias known as opportunistic pneumonias. They are caused by organisms that are harmless to people with healthy immune systems. Infecting organisms include:
- Pneumocystis carinii, renamed Pneumocystis jiroveci in 2002, is an atypical organism. Originally thought to be protozoa, it is now classified as a fungus. P. jiroveci is very common and generally harmless in people with healthy immune systems. It is the most common cause of pneumonia in AIDS patients.
Click the icon to see an image of pneumocystis carinii.
- Fungi, such as Mycobacterium avium
- Viruses, such as cytomegalovirus (CMV)
Click the icon to see an image of CMV.
In addition to AIDS, other conditions also put patients at risk for opportunistic pneumonia. They include cancers such as lymphoma and leukemia. Long-term use of corticosteroids and drugs known as immunosuppressants also increase the risk for these pneumonias.
Occupational and Regional Pneumonias
Exposure to chemicals can also cause inflammation and pneumonia. Where you work and live can put you at higher risk for exposure to pneumonia-causing organisms.
- Workers exposed to cattle, pigs, sheep, and horses are at risk for pneumonia caused by anthrax, brucella, and Coxiella burnetii, which causes Q fever.
Click the icon to see an image of inhalation anthrax.
- Agricultural and construction workers in the Southwest are at risk for coccidoidomycosis (Valley fever). The disease is caused by the spores of the fungus Coccidioides immitis.
- Those working in Ohio and the Mississippi Valley are at risk for histoplasmosis, a lung disease caused by the fungus Histoplasma capsulatum.
Click the icon to see an image of coccidoidomycosis.
- Workers exposed to pigeons, parrots, parakeets, and turkeys are at risk for psittacosis, a lung disease caused by the bacteria Chlamydia psittaci.
- Hantavirus, a rare virus carried by rodents, causes a dangerous form of lung disease. It does not spread from person to person. Cases have occurred in New Mexico, Arizona, California, Washington, and Mexico.
Click the icon to see an image of the hantavirus.
Severe Acute Respiratory Syndrome (SARS)
Severe acute respiratory syndrome (SARS) is a contagious respiratory infection that was recognized as a worldwide threat in 2003. It was first identified as a new disease by World Health Organization (WHO) physician Dr. Carlo Urbani. Urbani diagnosed SARS in a 48-year-old American businessman, who had traveled from the Guangdong province of China through Hong Kong to Hanoi, Vietnam. The businessman died from the illness. Dr. Urbani died from SARS just a month later, on March 29, 2003 at the age of 46. SARS spread fast. Within 6 weeks of Urbani's discovery, the disease had infected thousands of people around the world on every continent except Antarctica. Schools closed throughout Hong Kong and Singapore, and national economies were affected. The WHO officially identified SARS as a global health threat, and issued an unprecedented travel advisory. It wasn't clear at the time whether SARS would become a global pandemic or settle into a less aggressive pattern. The latter seems to have happened. As of a May 2005, there was no known SARS transmission anywhere in the world, according to the U.S. Centers for Disease Control and Prevention (CDC). The SARS outbreak is a dramatic example of how quickly world travel can spread a disease. According to reports from the CDC and WHO, more than 8,000 people became sick with SARS during the outbreak. Of that group, 774 died. The outbreak is also an example of how quickly a networked health monitoring system can respond to an emerging threat
Causes And Risk Factors. SARS is a serious form of atypical pneumonia that causes acute respiratory distress and sometimes death. It is caused by a new member of the coronavirus family, the family that includes the virus that causes the common cold). The discovery of the SARS-related virus represents one of the fastest identifications of a new organism in history.
SARS is spread by droplet contact. When someone with SARS coughs or sneezes, infected droplets are sprayed into the air. Like other coronaviruses, the SARS virus may live on hands, tissues, and other surfaces for up to 6 hours in these droplets and up to 3 hours after the droplets have dried. While droplet transmission through close contact has been responsible for most cases of SARS, there is evidence that SARS might also spread by infected droplets carried on hands and other objects the droplets had touched. Airborne transmission was a real possibility in some cases. Live virus had even been found in the stool of people with SARS, where it has been shown to survive for up to 4 days. And the virus may be able to live for months or years when the temperature is below freezing.
With other coronaviruses, re-infection (contracting the same disease after recovery or during initial illness) is common. Preliminary reports suggest that this may also be the case with SARS.
The estimated incubation period is 2 - 10 days, although there have been documented cases where the onset of illness was considerably faster or slower. People with active symptoms of illness are clearly contagious. It is not known, however, how early contagion begins before symptoms appear, or how long contagion might linger after the symptoms have disappeared.
Prevention. The best way to prevent SARS is to avoid direct contact with people who have SARS until 10 days after their fever and other symptoms are gone. Reduce travel to locations where there is an uncontrolled SARS outbreak. The CDC has identified hand hygiene as the cornerstone of SARS prevention. Wash your hands often with soap and water, or use an alcohol-based instant hand sanitizer. Cover your mouth and nose when sneezing or coughing. Consider respiratory secretions infectious. Clean commonly touched surfaces with an EPA-approved disinfectant. In some situations, masks, and goggles may be useful for preventing the spread of airborne or droplet infection. Gloves should be used in handling potentially infectious secretions.
Vaccine. In December 2004, the U.S. National Institutes of Health began a small clinical trial to test a preventive SARS vaccine. Interim results showed the vaccine to be safe and well tolerated. Chinese researchers began testing a SARS vaccine in May 2004.
Symptoms. The hallmark symptoms of SARS are fever of 100.4 F (38.0 C) or higher and a dry cough, with difficulty breathing or other respiratory symptoms. The following symptoms, listed in order of how often they appeared, were found in more than half of the first SARS patients:
- Fever
- Chills and shaking
- Muscle aches
- Cough
- Headache
Less common symptoms (also in order) include:
- Dizziness
- Cough that produces mucus (sputum)
- Sore throat
- Runny nose
- Nausea and vomiting
- Diarrhea
Signs and Tests. Listening to the chest with a stethoscope (auscultation ) may reveal abnormal lung sounds. In most people with SARS, progressive chest x-ray changes or chest CT changes reveal the presence of pneumonia.
Much attention was given early in the outbreak to the development of a quick, sensitive test for SARS. Specific tests for the SARS virus include the PCR for SARS virus, antibody tests to SARS (such as ELISA or IFA), and direct SARS virus isolation. All current tests have some limitations. General tests used in the diagnosis of SARS might include:
- Chest x-ray or chest CT is abnormal.
- CBC. People with SARS tend to have a low white blood cell count (leukopenia), a low lymphocyte count (lymphopenia), or a low platelet count (thrombocytopenia).
- Clotting profiles. SARS patients often have prolonged blood clotting times.
- Metabolic blood tests. Lactate dehydrogenase (LDH) and alanine transaminase (ALT) levels are often high. ALT and LDH are most often measured to evaluate the presence of tissue damage.
- CPK blood test. Creatine phosphokinase (CPK) is an enzyme found predominantly in the heart, brain, and skeletal muscle. Levels of the CPK enzyme are sometimes elevated in patients with SARS.
- Sodium and potassium blood tests are sometimes below normal levels.
Treatment. People suspected of having SARS should be evaluated immediately by a physician. Antibiotics are sometimes given in an attempt to treat bacterial causes of atypical pneumonia. Antiviral medications have also been used. High doses of steroids have been employed to reduce lung inflammation. In some serious cases, serum from people who have already gotten well from SARS (convalescent serum) has been given. Evidence of general benefit of these treatments has been inconclusive.
Other supportive care such as supplemental oxygen, chest physiotherapy, or mechanical ventilation is sometimes needed.
Prognosis. The overall worldwide death rate due to SARS at the end of the outbreaks was 14 - 15%, although it was up to 50% in infected people over age 65. Many more were sick enough to require breathing assistance from a machine (mechanical ventilation). Many others required ICU care.
Today, intensive public health policies are proving to be effective in controlling outbreaks. Many nations have stopped the epidemic within their own countries. All nations must be vigilant, however, to keep this disease under control.
Complications.
- Respiratory failure
- Liver failure
- Heart failure
- Myelodysplastic syndromes (bone marrow abnormalities leading to anemia, low platelet counts, and low white blood cell counts)
Call Health Care Provider. Call your health care provider if you suspect you or someone you have had close contact with has SARS.
Symptoms
General Symptoms. The symptoms of bacterial pneumonia develop very quickly and typically include:
- A single episode of shaking chills followed by fever
- Chest pain on the side of the infected lung. Severe abdominal pain sometimes occurs in people with pneumonia in the lower lobes of the lung.
- Shortness of breath
- Rapid breathing and heart beat
- Cough, which may be initially dry, but eventually produces sputum
- Nausea, vomiting, and muscle aches
Emergency Symptoms. Symptoms of pneumonia indicating a medical emergency include the following:
- High fever
- Rapid heart rate
- Bluish-toned (cyanotic) skin
- Labored and heavy breathing.
- Mental confusion
- Coughing up mucus (sputum) containing pus or blood
Symptoms in the Elderly. It is important to note that older people may have fewer or different symptoms than younger people. Symptoms may come on much more slowly. An elderly person who experiences even a minor cough and weakness for more than a day should seek medical help. Some elderly people may exhibit confusion, lethargy, and general deterioration.
Symptoms of Pneumonia Caused by Anaerobic Bacteria
Pneumonia caused by anaerobic bacteria such as prevotella (formerly called bacteroides) can produce dangerous abscesses in the lungs. People with such pneumonias may have prolonged fever and a productive cough. There is frequently blood in the mucus that is coughed up. Blood may indicate dead lung tissue. About a third of these patients experience weight loss.
Symptoms of Atypical Pneumonia
General Symptoms for Atypical Pneumonias. Atypical pneumonia is most commonly caused by mycoplasma and usually appears in children and young adults.
The disease progresses gradually.
- General flu-like symptoms often occur first. They may include fatigue, fever, weakness, headache, nasal discharge, sore throat, earache, and stomach and intestinal distress.
- Vague pain under and around the breastbone may occur, but the severe chest pain associated with typical bacterial pneumonia is uncommon.
- Patients may have a severe hacking cough, but it usually does not produce sputum.
Symptoms of Legionnaire Disease. Symptoms of Legionnaire disease usually occur more rapidly and include high fever, a dry cough, and shortness of breath. These symptoms are often accompanied by headache, muscle pains, fatigue, gastrointestinal problems, and mental confusion.
Prognosis
More than a million people are hospitalized each year for pneumonia, making it the third most frequent cause of hospitalizations (births are first, and heart disease is second). Although the majority of pneumonias respond well to treatment, the infection kills 40,000 - 70,000 people each year.
Outlook for High-Risk Individuals
Hospitalized Patients. For patients who require hospitalization for pneumonia, the death rate is 10 - 25%. If pneumonia develops in patients already hospitalized for other conditions, death rates range from 50 - 70%, and are higher in women than in men.
Older Adults. Community-acquired pneumonia is responsible for 350,000 - 620,000 hospitalizations in the elderly every year. Older adults have lower survival rates than younger people. Even when older individuals recover from CAP, they have higher-than-normal death rates over the next several years. Elderly people who live in nursing homes or who are already sick are at particular risk.
Very Young Children. About 20% of deaths in stillborn and very young infants are due to pneumonia. Small children who develop pneumonia and survive are at risk for developing lung problems in adulthood.
Pregnant Women. Pneumonia poses a special hazard for pregnant women, possibly due to changes in a pregnant woman's immune system. This complication can lead to premature labor and increases the risk of death during pregnancy.
Patients With Impaired Immune Systems. Pneumonia is particularly serious in people with impaired immune systems. This is particularly true for AIDS patients, in whom pneumonia causes about half of all deaths.
Patients With Serious Medical Conditions. Pneumonia is also very dangerous in people with diabetes, cirrhosis, sickle cell disease, cancer, and in those whose spleens have been removed.
Risk by Organisms
Specific organisms vary in their effects. Mild pneumonia is usually associated with the atypical organisms mycoplasma and chlamydia. Severe pneumonia is most often associated with a wide range of organisms. Some are very virulent (potent) but are extremely curable, while others are difficult to treat.
- Mycoplasma and chlamydia are the most common causes of mild pneumonias and are most likely to occur in children and young adults. They rarely require hospitalization when they are appropriately treated, although recovery may still be prolonged. Severe and life-threatening cases are more likely to occur in elderly people with other medical conditions.
- Streptococcus pneumoniae is the most common cause of pneumonia and, in fact, all bacterial upper respiratory infections. It can produce severe pneumonia, with mortality rates of 10%. Nevertheless, pneumococcal pneumonia is very responsive to many antibiotics.
- Staphylococcus aureus is a Gram-positive bacterium that often causes severe pneumonia in hospitalized and high-risk patients and following influenza A and B. People who get this form of pneumonia may develop pockets of infection in their lungs (abscesses) that are difficult to treat and can cause the death of lung tissue (necrosis). Mortality rates are 30 - 40%, in part because the patients who develop this infection are generally very ill or vulnerable.
- Pseudomonas aeruginosa and Klebsiella pneumoniae are Gram-negative bacteria that pose a risk for abscesses and severe lung tissue damage.
- Legionella pneumophila is very virulent and can cause widespread damage. Treatments have improved dramatically since it was first identified. However, a 2002 study suggested that many patients experience long-term problems, including coughing, shortness of breath, fatigue, and neurological and muscular complications.
- Viral pneumonia is usually very mild, but there are exceptions. Respiratory syncytial virus (RSV) pneumonia rarely poses a danger for healthy young adults, but it can be life-threatening in infants and serious in the elderly.
Complications of Pneumonia
Abscess. An abscess in the lung is a thick-walled, pus-filled cavity that forms when infection has destroyed lung tissue. It typically occurs as a result of aspiration pneumonia, when a mixture of organisms is carried into the lung. Untreated abscesses can cause hemorrhage (bleeding) in the lung, but targeted antibiotic therapy significantly reduces their danger. Abscesses are more common with Staphylococcus aureus, Pseudomonas aeruginosa, or Klebsiella pneumoniae, and uncommon with Streptococcus pneumoniae.
Respiratory Failure. Respiratory failure is one of the top causes of death in patients with pneumococcal pneumonia. Acute respiratory distress syndrome (ARDS) is the specific condition that occurs when the lungs are unable to function and oxygen is so severely reduced that the patient's life is at risk. Failure can occur if pneumonia leads to mechanical changes in the lungs (ventilatory failure) or oxygen loss in the arteries (hypoxemic respiratory failure).
Bacteremia. Bacteremia, bacteria in the blood, is the most common complication of pneumococcus infection, although it rarely spreads to others sites. Bacteremia is a frequent complication of infection from Gram-negative organisms, including Haemophilus influenzae.
Pleural Effusions and Empyema. The pleura are two thin membranes that line the chest and lungs:
- The visceral pleura cover the lungs.
- The parietal pleura cover the chest wall.
In some cases of pneumonia the pleura become inflamed, which can result in breathlessness and acute chest pain when breathing.
In about 20% of pneumonia cases fluid builds up between the pleural membranes, a condition known as pleural effusion. Ordinarily, the narrow zone between the two membranes contains only a tiny amount of fluid, which lubricates the lungs.
In most cases, particularly in Streptococcus pneumoniae, the fluid remains sterile (no bacteria are present), but occasionally it can become infected and even filled with pus, a condition called empyema. Empyema is more likely to occur with specific organisms such as Staphylococcus aureus or Klebsiella pneumoniae infections. The condition can cause permanent scarring.
Collapsed Lung. In some cases, air may fill up the area between the pleural membranes, causing the lungs to collapse. This is called pneumothorax. It may be a complication of pneumonia (particularly Streptococcus pneumoniae ) or of the invasive procedures used to treat pleural effusion.
Other Complications of Pneumonia. In rare cases, infection may spread from the lungs to the heart and possibly throughout the body. This can cause abscesses in the brain and other organs. Severe hemoptysis (coughing up blood) is another potentially serious complication of pneumonia, particularly in patients with lung problems such as cystic fibrosis.
Kidney complications and electrolyte imbalances are common in patients admitted to the hospital with pneumonia. If not treated, these problems cause more severe illness and increase the risk of death. Treatment with intravenous saline can usually resolve the problem.
Long Term Effects of Atypical Pneumonias
The pneumonias cased by the atypical organisms mycoplasma and chlamydia are usually mild. Some research suggests, however, that chlamydia may have powerful inflammatory effects in the blood vessels. This effect may have certain adverse long-term consequences even in healthy younger individuals.
Heart Disease and Stroke. Research has suggested that chlamydia may trigger the immune system to react, causing inflammation in the coronary arteries. Over time, this can cause hardening of the arteries (atherosclerosis). Atherosclerosis can lead to heart attacks and strokes. Studies on a causal relationship between chlamydia and heart disease have been mixed.
Click the icon to see an image of arterial plaque.
Chylamydia pneumoniae has been associated with a thickening in the carotid arteries that lead to the brain -- a risk factor for stroke. It is not clear whether the organism poses any significant risk for stroke.
Click the icon to see an image of atherosclerosis of the internal carotid artery.
Asthma. Chlamydia pneumoniae, Mycoplasma pneumoniae, and RSV are becoming suspects in many cases of severe adult asthma. One small Australian study found evidence of previous chlamydia infection in 64% of the asthmatic patients tested.
Risk Factors
Risk factors for pneumonia often depend on the specific type of disease.
Risk Factors for Community-Acquired Pneumonia (CAP)
CAP is the most common type of pneumonia. It develops outside of the hospital. Each year 2 - 4 million people in the US develop CAP, and 600,000 are hospitalized. The elderly, infants, and young children are at greatest risk for the disease.
Risk Factors for Hospital-Acquired (Nosocomial) Pneumonia
Pneumonia that is contracted in the hospital is called hospital-acquired or nosocomial pneumonia. It affects an estimated 5 -10 of every 1,000 hospitalized patients every year. More than half these cases may be due to strains of bacteria that have developed resistance to antibiotics. In fact, methicillin-resistant Staphyllococcus aureus and multidrug-resistant Pseudomonas aeruginosa are leading causes of death from hospital-acquired pneumonia. The elderly, the very young, and those with chronic or severe medical conditions, are at highest risk.
In addition, the following conditions within the hospital put patients at higher risk:
- Surgery, particularly in people over the age of 80. Among the surgical procedures that pose a particular risk are splenectomy (removal of the spleen), abdominal aortic aneurysm repair, or operations that impair coughing.
- Being in the intensive care unit (ICU). This is particularly true for newborns or patients on breathing machines (mechanical ventilators). In one study, 10% of ICU patients on a breathing machine developed pneumonia. Such patients who lie flat on their backs are at particular risk for aspiration pneumonia. Raising the patient up may reduce this risk.
- Sedation. Hospital patients who receive sedatives also have a higher risk of developing nosocomial pneumonia.
- Previous use of antibiotics, particularly within 6 months.
Hospitalized patients are particularly vulnerable to Gram-negative bacteria and staphylococci, which can be especially dangerous in people who are already ill.
Medical Conditions that Pose Risks for Pneumonia
Chronic Lung Disease. Chronic obstructive lung diseases (COPD), which include chronic bronchitis and emphysema, affect 15 million people in the U.S. This condition is a major risk factor for pneumonia. In patients with COPD, vaccination with the pneumococcal vaccine can substantially reduce the risk of developing pneumonia or decrease its severity.
Click the icon to see an image of emphysema.
People With Compromised Immune Systems. People with impaired immune systems are extremely susceptible to pneumonia. It is a common problem in people with HIV and AIDS. In one study, the primary bacteria were found to be Legionella pneumophilia and Streptococcus pneumoniae. Smoking and chemotherapy for cancer were more common in those with legionella pneumonia. The patients tended to have a higher CD4 count, undetectable viral load, and more frequent need for antiretroviral therapy. Their pneumonia was more severe than in HIV patients diagnosed with pneumococcal pneumonia. Those with legionell were more likely to have respiratory failure, need ventilation, have pneumonia in both lungs, and were more likely to die. However, AIDS was more common in the patients with pneumococcal pneumonia.
In addition to AIDS, other conditions that compromise the immune system include organ transplantation, chemotherapy, and adult and pediatric cancers, especially leukemia and Hodgkin's lymphoma. Patients who are on corticosteroids or other medications that suppress the immune system are also prone to infection.
Gastroesophageal Reflux Disease. Gastroesophageal reflux disease (GERD) is a condition in which acids from the stomach move up into the esophagus. This is called reflux. Current studies indicate an association between GERD and various problems that occur in the sinuses, ears, nasal passages, and airways of the lung. People with GERD appear to have an above-average risk for chronic bronchitis, chronic sinusitis, emphysema, pulmonary fibrosis (lung scarring), and recurrent pneumonia. If a person inhales fluid (aspirates) from the esophagus into the lungs, serious pneumonia can occur. GERD may contribute to these conditions by triggering inflammation in these upper passages.
However, GERD drugs may increase one's risk. Patients at high risk for pneumonia should take gastric acid-suppressing drugs only when necessary and at the lowest possible dose. A 2004 study found that the use of gastric acid-suppressing drugs raises the risk of developing CAP. The highest risks were associated with proton pump inhibitors (PPIs) such as Prilosec and Nexium, but H2-receptor antagonists such as Tagamet and Pepcid also elevated risk. The researchers theorize that reducing levels of germ-killing stomach acid allow germs to spread in the upper gastrointestinal tract and move into the respiratory tract. The risk posed by these medications is highest in the elderly, children, and patients with asthma, COPD, and compromised immune systems.
Acute stroke. Acute stroke is a risk factor for developing pneumonia. In one German study, the incidence of stroke-associated pneumonia (SAP) was 22% in patients admitted to the intensive care following a stroke. Dysphagia, non-lacunal basal-ganglia infarction, or any infection present on admission, and National Institutes of Health Stroke Scale score greater than or equal to 10 were found to be independent risk factors for the development of SAP. Other risk factors included combined brainstem and cerebellar infarction, infarction affecting more than 66% of the middle cerebral arterial territory, hemispheric infarction exceeding middle cerebral artery territory, impaired vigilance, mechanical ventilation, age of 73 or greater, and cardioembolic stroke. Patients with lacunal strokes were found to be at less risk of SAP.
Click the icon to see an image of gastric reflux.
Factors Associated with a Higher Risk in Healthy Adults
Dormitory or Barrack Conditions. Recruits on military bases and college students living in dormitories are at higher than average risk for Mycoplasma pneumonia. These groups are at lower risk, however, for more serious types of pneumonia.
Smoke and Environmental Pollutants. The risk for pneumonia in people who smoke more than a pack a day is three times that of nonsmokers. Those who are chronically exposed to secondhand cigarette smoke, which can injure airways and damage the cilia, are also at risk. Quitting smoking reduces the risk of dying from pneumonia to normal, but the full benefit takes 10 years to be realized. Toxic fumes, industrial smoke, and other air pollutants may also damage cilia function, which is a defense against bacteria in the lungs.
Drugs and Alcohol. Alcohol or drug abuse is strongly associated with pneumonia. These substances act as sedatives and can diminish the reflexes that trigger coughing and sneezing. Alcohol also interferes with the actions of macrophages, the white blood cells that destroy bacteria and other microbes. Intravenous drug abusers are at risk for pneumonia from infections that originate at the injection site and spread through the bloodstream to the lungs.
Fatty Diet: A diet high in fatty acids such as palm oils appears to increase the risk of CAP in young and middle-aged women by as much as 54%. Higher intake of monosaturated fats appears to decrease the risk of pneumonia.
Specific Risk Factors for Recurrent Pneumonia in Children
Certain children have a higher-than-normal risk for pneumonia and recurrence. Conditions that predispose infants and small children to pneumonia include:
- Impaired immune system
- Leukemia
- Infection with the respiratory syncytial virus (RSV)
- Gastroesophageal reflux disorder
- Inborn lung or heart defects
- Abnormalities in muscle coordination of the mouth and throat
- Asthma
- Certain genetic disorders such as sickle-cell disease, cystic fibrosis, and Kartagener's syndrome, which result in poorly functioning cilia, the hair-like cells lining the airways
Diagnosis
Diagnostic Difficulties in Community-Acquired Pneumonia (CAP). It is important to determine whether the cause of CAP is a bacterium, atypical bacterium, or virus, since they require different treatments. In children, for example, S. pneumonia is the most common cause of pneumonia, but respiratory syncytial virus may also cause the disease. Although symptoms may differ, they often overlap, which can make it difficult to identify the organism by symptoms alone.
Nevertheless, in many cases of mild-to-moderate CAP, the physician is able to diagnose and treat pneumonia based solely on a history and physical examination.
Diagnostic Difficulties with Hospital-Acquired (Nosocomial) Pneumonia. Diagnosing pneumonia is particularly difficult in hospitalized patients for a number of reasons:
- Many hospitalized patients have similar symptoms, including fever or signs of lung infiltration on x-rays.
- In hospitalized patients, sputum or blood tests often indicate the presence of bacteria or other organisms, but such agents do not necessarily indicate pneumonia.
Doctors making a diagnosis of pneumonia should rule out other conditions, using a chest x-ray, two sets of blood cultures, a urine analysis for legionella, and a lung fluid sample, among other tests.
Medical and Personal History
The patient's history is an important part of making a pneumonia diagnosis. Patients should be sure to report any of the following:
- Recent or chronic respiratory infection
- Exposure to people with pneumonia or other respiratory illnesses (such as tuberculosis)
- History of smoking
- Alcohol or drug abuse
- Recent travel
- Occupational risks
Physical Examination
Use of the Stethoscope. The most important diagnostic tool for pneumonia is the stethoscope. Sounds in the chest that may indicate pneumonia include:
- Rales, a bubbling or crackling sound. Rales on one side of the chest or heard while the patient is lying down are strongly suggestive of pneumonia.
- Rhonchi, abnormal rumblings indicating the presence of thick fluid.
- A dull thud obtained by percussion. The physician will also use a test called percussion, in which the chest is tapped lightly. A dull thud, instead of a hollow drum-like sound, indicates certain conditions suggestive of pneumonia. These conditions include including consolidation (a condition in which the lung becomes firm and inelastic), and pleural effusion (fluid build-up in the space between the lungs and the lining around it).
Laboratory Tests for Diagnosing Infection and Identifying Bacteria
Although current antibiotics can destroy a wide spectrum of organisms, it is best to use an antibiotic that targets the specific one making a person sick. Unfortunately, people carry many bacteria, and sputum and blood tests are not always effective in distinguishing between harmless and harmful kinds.
In severe cases, a doctor needs to use invasive diagnostic measures to identify cause of the infection. Standard lab tests used to help diagnose pneumonia include:
Sputum Tests. The color of the mucus (sputum) sample coughed up from the lungs can reveal the severity of the disease. Only a sputum sample will reveal the infecting organism.
The patient coughs as deeply as possible to bring up mucus from the lungs, since a shallow cough produces a sample that usually only contains normal mouth bacteria. Some people may need to inhale a saline spray to produce an adequate sample. In some cases, a tube will be inserted through the nose into the lower respiratory tract to induce a deeper cough.
The physician will check the sputum for:
- Blood, which means an infection is present
- Color and consistency: If it is yellow, green, or brown, an infection is likely.
The sputum sample is sent to the laboratory, where it is analyzed for the presence of bacteria and to determine whether the bacteria are gram-negative or Gram-positive.
Blood Tests. The following blood tests may be performed:
- White blood cell count (WBC). High levels indicate infection.
- Blood cultures. Cultures are done to determine the specific organism causing the pneumonia, but they usually can not distinguish between harmless and dangerous organisms. They are accurate in only 10 - 30% of cases. Their use is generally limited to severe cases.
- Detection of antibodies to S. pneumoniae. Antibodies are immune factors that target specific foreign invaders. One type of immunohistochemical test for S. pneumoniae is showing tremendous promise.
- Polymerase Chain Reaction (PCR). In some difficult cases, PCR may be performed. A test makes multiple copies of the genetic material (RNA) of a virus or bacteria to make it detectable.
- Procalcitonin test. This marker of systemic inflammatory response to infection is increasingly recognized as a valuable method of determining which patients need antibiotics, and when antibiotic therapy can be safely stopped. Such information is critical to preventing the development of antibiotic-resistant bacteria.
Urine Tests. Urinary antigen tests for Legionella pneumophila and Streptococcus pneumoniae may be performed in patients with severe CAP. The S. pneumoniae test takes only 15 minutes and may identify up to 77% of pneumonia cases and rule out S. pneumoniae infection in 98% of patients. It may not be useful in children.
Invasive Tests. In critically-ill patients with ventilator-associated pneumonia, physicians have tried sampling fluid taken from the lungs or trachea. The techniques enabled the physicians to identify the pneumonia-causing bacteria and start the appropriate antibiotics. However, this made no difference in the length of stay in the ICU or hospital, and there was no significant difference in outcome.
Laboratory Tests for Less Common Organisms
If uncommon organisms -- such as legionella, mycoplasma, and chlamydia -- are strongly suspected, more advanced laboratory tests may be used:
- Specialized techniques can detect antibodies to the organisms in blood samples, but these antibodies, such as those responding to mycoplasma or chlamydia, are not present early enough in the course of pneumonia to permit prompt diagnosis and treatment.
- PCR is useful for identifying certain atypical strains, including mycoplasma and Chlamydiapneumoniae and, possibly, Haemophilus influenzae type b, but it is expensive.
- A urine test can be used to diagnose some cases of Legionnaire disease.
- Specialized tests called DNA probes are being developed to detect these organisms in respiratory secretions.
Chest X-Rays and Other Imaging Techniques
X-Rays. A chest x-ray is nearly always taken to confirm a diagnosis of pneumonia.
A chest x-ray may reveal the following:
- White areas in the lung called infiltrates, which indicate infection
- Complications of pneumonia, including pleural effusions and abscesses
Other Imaging Tests. Computed tomography (CT) scans or magnetic resonance imaging (MRI) scans may be useful in some circumstances, especially when:
- X-ray results are unclear
- Patients do not respond to antibiotics
- Complications occur
- Patients have other serious health problems
Click the icon to see an image of a CT scan.
CT and MRI can help detect the presence of tissue damage, abscesses, and enlarged lymph nodes. They can also detect some tumors that block bronchial tubes. No imaging technique can determine the actual organism causing the infection. However, features on CT scan of patients with certain forms of pneumonia -- for example, that caused by Legionella pneumophila -- are usually different from features produced by other bacteria in the lungs.
Invasive Diagnostic Procedures
Invasive diagnostic procedures may be required when:
- Patients have life-threatening complications
- Standard treatments have failed for no known reason
- AIDS or other immune problems are present
Invasive procedures include:
Thoracentesis. If a doctor detects pleural effusion during the physical exam or on an imaging study, and suspects that empyema (pus) is present, a thoracentesis is performed.
- Fluid in the pleura is withdrawn using a long thin needle inserted between the ribs.
- The fluid is then sent to the lab for multiple tests.
Complications of this procedure are rare, but can include collapsed lung, bleeding, and introduction of infection.
Bronchoscopy. A bronchoscopy is done in the following way:
- The patient is given a local anesthetic, supplementary oxygen, and sedatives.
- The physician inserts a fiber optic tube into the lower respiratory tract through the nose or mouth.
- The tube acts like a telescope into the body, allowing the physician to view the windpipe and major airways and look for pus, abnormal mucus, or other problems.
- The doctor removes specimens for analysis and can also treat the patient by removing any foreign bodies or infected tissue encountered during the process.
Click the icon to see an image of bronchoscopy.
Bronchoalveolar lavage (BAL) may be done at the same time as bronchoscopy. This involves injecting high amounts of saline through the bronchoscope into the lung and then immediately sucking the fluid out. The fluid is then analyzed in the laboratory. Studies find BAL to be an effective method for detecting specific infection-causing organisms.
The procedure is usually very safe, but complications can occur. They include allergic reactions to the sedatives or anesthetics, asthma attacks in susceptible patients, and bleeding. Fever may follow the procedure.
Lung Biopsy. In very severe cases of pneumonia or when the diagnosis is unclear, particularly in patients with damaged immune systems, a lung biopsy may be required. A lung biopsy involves taking some tissue from the lungs and examining it under a microscope.
Lung Tap. This procedure typically uses a needle inserted between the ribs to draw fluid out of the lung for analysis. It is known by a number of names including lung aspiration, lung puncture, thoracic puncture, transthoracic needle aspiration, percutaneous needle aspiration, and needle aspiration. It is a very old procedure that is not done often any more, since it is invasive and poses a slight risk for collapsed lung. Some experts argue, however, that a lung tap is more accurate than other methods for identifying bacteria, and the risk it poses is slight. Given the increase in resistant bacteria, they believe its use should be reconsidered in young people.
Ruling Out Other Disorders that Cause Coughing or Affect the Lung
Common Causes of Persistent Coughing. Over 30 million people seek medical help each year for persistent coughing, which is nearly always temporary and harmless when other symptoms, such as fever, are not present. The four most common causes of persistent coughing are asthma, postnasal drip, gastroesophageal reflux disease (GERD), and chronic bronchitis. Other obvious common causes of chronic cough include heavy smoking or the use of heart drugs known as ACE inhibitors.
Acute Bronchitis. Acute bronchitis is an infection in the passages that carry air from the throat to the lung. The infection causes a cough that produces phlegm. Acute bronchitis is almost always caused by a virus and usually clears up on its own within a few days. In some cases, acute bronchitis caused by a cold can last for several weeks.
Chronic Bronchitis. Chronic bronchitis causes shortness of breath and is often accompanied by infection, mucus production, and coughing, but it is a long-term and irreversible condition. The same microbes that cause pneumonia can cause chronic bronchitis, and symptoms of the two disorders are often similar. They include fatigue, coughing, fever, and production of sputum. There are significant differences between chronic bronchitis and pneumonia:
- Patients with bronchitis are less likely to have wheezing, shortness of breath, chills, very high fevers, and other signs of severe illness.
- Those with pneumonia usually cough up heavy sputum, which is also more likely to contain blood.
- X-rays of patients with bronchitis do not show fluid or consolidation in the lung.
Asthma. In asthma, the cough is accompanied by wheezing and occurs mostly at night or during activity. Fever is rarely present (unless the patient also has an infection). Asthmatic symptoms from occupational causes can cause persistent coughing, which is usually worse during the work week. Tests -- the methacholine inhalation challenge and pulmonary function studies -- may be effective in diagnosing asthma.
Anthrax. Because of current terrorist concerns, it is important to differentiate between anthrax and community-acquired pneumonia. According to one study, people with inhalation anthrax are more likely to have rapid heart rate and less likely to have headache, nasal symptoms, and muscle aches than those with pneumonia. Blood tests with anthrax also show high hematocrit and low albumin and sodium levels. Certain chest x-ray findings also raise the likelihood of anthrax.
Other Disorders that Affect the Lung. Many conditions mimic pneumonia, particularly in hospitalized patients. They include:
- Tuberculosis
- Bronchial asthma
- Bronchiectasis, an irreversible widening of the airways usually associated with birth defects, chronic sinus or bronchial infection, or blockage
- Atelectasis, a collapse of lung tissue
- Heart failure. If it affects the left side of the heart, fluid build-up can occur in the lungs and cause persistent cough, shortness of breath, and wheezing.
- Severe allergic reactions, such as reactions to drugs
- Acute respiratory distress syndrome (ARDS)
- Lung cancer
- Interstitial pulmonary fibrosis, a non-infectious inflammation of the lung marked by progressive damage and scarring
Ruling Out Causes in Children. Important causes of coughing in children at different ages include:
- Asthma
- Physical abnormalities in infants under 18 months
- Sinusitis in children 18 months to 6 years
- Psychologic causes in older children and adolescents
What Is Acute Bronchitis?
Acute bronchitis is an infection in the passages that carry air from the throat to the lung. In such cases, the airway tubes become inflamed and collect mucus, causing a cough that produces phlegm. In 95% of cases, acute bronchitis is caused by a virus and is spread from person to person through coughing. In some cases, mycoplasma or chlamydia may be responsible.
Symptoms. The cough in acute bronchitis usually lasts for 7 - 10 days. In about half of patients, coughing can last for up to 3 weeks, and 25% of patients continue to cough for more than one month.
Complications. Acute bronchitis is usually temporary. It can last for weeks to months if the airways are not healing properly. Pneumonia should be suspected if coughing is continuous and hacking, if blood appears in the sputum, and if the patient has a high fever and signs of severe illness. These signs include shortness of breath or extreme weakness and fatigue. [See In-Depth Report #94: Colds and the flu. ]
Of particular interest and some concern are the roles of mycoplasma and chlamydia, two of the infectious organisms that cause acute bronchitis. These agents are being investigated for their roles as possible causes of asthma. Chlamydia is also being investigated as a trigger for coronary artery disease.
Treatments.
- Bronchodilators. For some patients with acute bronchitis, inhaled medications called bronchodilators may be effective. These drugs relax and open the airways and may relieve symptoms and reduce the duration of the coughing. The most common bronchodilator used for acute bronchitis is albuterol (Proventil, Ventolin). It is called salbutamol outside the US. The drug is a short-acting beta-2 agonist.
- Antibiotics. Acute bronchitis almost never warrants antibiotics. (Coughing caused by pneumonia, however, does require antibiotics.) A 5-year study of more than 800 patients found that those with uncomplicated acute bronchitis all recovered within the same time period, regardless of whether or not they received antibiotics. For most patients, coughing lasted an average of 12 days. For a quarter of the patients, coughing lasted 17 days.
Treatment
Patients with pneumonia are generally treated with:
- Antibiotics
- Respiratory support with oxygen, if needed
Categorizing Severity and Determining the Need for Hospitalization
Up to 10% of all adult hospitalizations in the U.S. are due to pneumonia. Studies indicate that many patients are hospitalized unnecessarily for pneumonia, and those patients could be released sooner. A number of strategies are being devised to determine when and which patients can be safely discharged. Studies have shown that low-risk patients with mild-to-moderate pneumonia do just as well when treated as outpatients and return to work and normal activities faster than those treated in the hospital.
One approach for determining whether a patient should be hospitalized categorizes patients into 5 classes depending on risk factors for severity, with class 1 being the least severe (having less than a 0.5% risk for death) and class 5 being the most severe (having at least a 10% risk of death).
Ruling out the Least Severe Cases. The procedure for determining the need for hospitalization starts by selecting patients in the lowest risk groups (classes 1 and 2) who can be discharged with outpatient care only. This can often be done with a simple physical examination, which can rule out a severe condition. Patients in low-risk categories have the following characteristics:
- Under age 50 and not a patient in a nursing home
- No other major illnesses
- No serious symptoms such as altered mental state, breathing problems, bluish skin, very low blood pressure, or very high fever
Even these criteria, however, are flexible. Physicians must use their own judgment and take all factors into consideration. As examples, the following young people with signs of pneumonia should be hospitalized, even if they otherwise fit low-risk (class 1) categories:
- Any infant under the age of one month
- Young adults with alcoholism or severe psychiatric condition
- Young adults or children with abnormal heart rhythm
- Young adults or children who are vomiting heavily
- Children who are dehydrated
Determining The Next Levels of Severity. If a patient is not in a class 1 category or does not appear to need hospitalization, the next step is to determine which of the other 4 higher classes the patient fits into. This step involves assigning points to other findings, including:
- Laboratory test results
- X-ray findings
- Demographics (Is the patient male or female? Does the patient live in a nursing home?)
The points are added and the patients are scored:
- Patients who score the lowest are assigned class 2 and 3. They can usually be treated at home or need only to be hospitalized for 24 hours for observation.
- Patients with higher scores are placed in classes 4 and 5, and are hospitalized.
Home care may be possible even in severe cases when there is good support and available home nursing services. Often, caregivers can even be trained to administer intravenous antibiotics and chest therapy to patients at home.
Home Treatment
Joint guidelines issued in 2007 by the Infectious Disease Society of America and the American Thoracic Society (ITSA/ATS) recommend that mild CAP in otherwise healthy patients be treated with oral macrolide antibiotics (azithromycin, clarithromycin, or erythromycin).
Many patients with heart disease, kidney disease, diabetes, or other comorbid conditions may still be treated as outpatients. However, they should be given a fluoroquinolone (moxifloxacin, gemifloxacin, or levofloxacin) or a beta-lactam (preferably high-dose amoxicillin or amoxicillin-clavulanate), plus a macrolide, unless they live in an area with high S. pneumoniae resistance to macrolides.
The following tips are also suggested:
- Drink plenty of liquids.
- Do not suppress a cough. Coughing is an important reflex for clearing the lungs. Some doctors advise taking expectorants, such as guaifenesin (Breonesin, Glycotuss, Glytuss, Hytuss, Naldecon Senior EX, Robitussin) to loosen mucus. However, there is no proof that any of these products make much difference in outcome.
- Mild pain can be treated with aspirin (in adults only), acetaminophen (Tylenol), or ibuprofen (Advil, Motrin).
- For severe pain, codeine or other stronger pain reliever may be prescribed. It should be noted, however, that codeine and other narcotics suppress coughing, so they should be used with care in pneumonia. Such pain relievers often require monitoring.
- A laboratory study reported that aromatic oils containing oregano, thyme, and rosewood destroyed S. pneumoniae. It is not known whether they have any effect on pneumonia in people.
- Patients should practice chest therapy.
Hospitalization Guidelines
Treatment. If the pneumonia is severe enough for hospitalization, the standard treatment is intravenous administration of antibiotics for 5 - 8 days. In cases of uncomplicated pneumonia, many patients may require only 2 or 3 days of intravenous antibiotics followed by oral therapy. Antibiotics taken by mouth are prescribed when the patient has improved substantially or leaves the hospital.
ITSA/ATS guidelines recommend patients admitted to the hospital (but not the ICU) be treated with fluoroquinolones or a beta-lactam plus a macrolide (preferably cefotaxime or ceftriaxone and ampicillin).
Duration of Stay. Patients should remain in hospital until all their vital signs are stable. Most patients become stabilized in 3 days. Many experts use 7 variables to measure stability and to determine whether the patient can go home:
- Temperature. (Some experts believe that patients can go home when their temperature drops to 101 F. Stricter criteria require that it be at or close to 98.6 F.)
- Respiration rate. (Goal is a normal breathing rate, although expert opinion differs on the degree of normality required to be discharged.)
- Heart rate. (Goal is 100 beats per minute or less.)
- Blood pressure. (Goal is systolic blood pressure of 90 mmHg or greater.)
- Oxygenation. (Goal is determined by the physician.)
- The ability to eat. (Goal is regular appetite.)
- Mental function. (Goal is normal.)
Patients or their families should discuss these criteria with their doctor. In a 2002 study, 42% of patients who had 2 or more signs of instability when they left the hospital were either readmitted or died within 30 days, compared with 10.5% of completely stabilized patients.
Chest Therapy
Chest therapy using incentive spirometry, rhythmic inhalation and coughing, and chest tapping are all important techniques to loosen the mucus and move it out of the lungs. It should be used both in the hospital and during recovery at home.
Incentive Spirometry. The patient uses an incentive spirometer at regular intervals to improve breathing and loosen sputum. The spirometer is a hand-held clear plastic device that includes a breathing tube and a container with a movable gauge. The patient exhales and then inhales forcefully through the tube, using the pressure of the inhalation to raise the gauge to the highest level possible.
Rhythmic Breathing and Coughing. During recovery, the patient performs rhythmic breathing and coughing every 4 hours:
- Before starting the breathing exercise, the patient should tap lightly on the chest to loosen mucus within the lung. If available, a caregiver should also tap on the patient's back.
- The patient inhales rhythmically and deeply 3 or 4 times.
- The patient then coughs as deeply as possible with the goal of producing sputum.
Medications
Dozens of antibiotics are available for treating pneumonia, but selecting the best drug is sometimes difficult. Patients with pneumonia need an antibiotic that is effective against the organism causing the disease. When the organism is unknown, "empiric therapy" is given, meaning the doctor guesses which antibiotic is likely to work based on factors such as the patients' age, health, and severity of the illness.
In determining the appropriate antibiotic, the physician must first answer a number of questions:
- How severe is the pneumonia? Mild-to-moderate cases can be treated at home with oral antibiotics, while severe pneumonia usually requires intravenous antibiotics administered in the hospital.
- If the organism causing the pneumonia is not known, was the disorder community- or hospital-acquired? Different organisms are usually involved in each setting, and the physician can use this information to guess the most likely organism causing the pneumonia.
- If the organism is known, is it typical or atypical? Community-acquired pneumonias, for example, are usually caused by the typical bacteria Streptococcus pneumoniae, Haemophilus influenzae, or Moraxella catarrhalis, which have traditionally been treated with penicillin or other standard antibiotics. These antibiotics do not affect atypical organisms, such as legionella, mycoplasma, or chlamydia. These organisms are generally treated with a macrolide or possibly a newer quinolone.
- Does the patient have an impaired immune system? Antibiotics used to treat such patients may differ from those used in patients with healthy immune systems.
Once an antibiotic has been chosen, there are still difficulties:
- Individuals respond differently to the same antibiotic, depending on age, health, size, and other factors.
- Patients can be allergic to certain antibiotics, thus requiring alternatives.
- Patients may harbor strains of bacteria that are resistant to certain antibiotics.
Antibiotic Treatments for Community-Acquired Pneumonia
For a more detailed discussion of the different types of antibiotics, see the "Antibiotic Classes" section below.
Many cases of community-acquired pneumonia are caused by S. pneumoniae, Gram-positive bacteria that usually respond to antibiotics known as beta-lactams (which include penicillin,) and to macrolides. However, resistant strains of S. pneumoniae are increasingly common. Most resistant strains respond to fluoroquinolines such as levofloxacin (Levaquin), gemifloxacin (Factive) or moxifloxacin (Avelox), or to ketolides (telithromycin).
In addition, other important causes of CAP, particularly in younger people, are atypical bacteria, which respond to macrolides (erythromycin, clarithromycin, or azithromycin), to ketolides, or to newer fluoroquinolones.
Antibiotic treatment for CAP is determined by a number of factors, including the patient's history of antibiotic therapy, co-existing diseases (such as COPD, diabetes, and heart failure), and whether the patient is well enough to be treated at home or requires hospitalization or nursing home care. Treatment options can include a single drug, such as levofloxacin or doxycycline, or combination treatment, such as a macrolide administered with a beta-lactam.
Antibiotics taken by mouth are generally sufficient for patients whose CAP is mild enough to be treated at home. Intravenous antibiotics are required for hospitalized patients with CAP. Antibiotic therapy should be given for a minimum of 5 days -- longer if the patient still has a fever and more than one sign of clinical instability.
Antibiotic Treatments for Hospital-Acquired (Nosocomial) Pneumonia
Gram-Positive Pneumonia. S. aureus is a common cause of hospital-acquired pneumonia and is a potentially life-threatening infection. Resistance to penicillin is the rule in these cases, but certain specialized penicillins such as nafcillin may be effective. The alternatives to penicillins are first- or second generation cephalosporins. Unfortunately, resistance to these agents is increasing as well. Vancomycin is used for highly resistant bacteria.
Gram-Negative Pneumonia. Patients with hospital-acquired pneumonia are at high risk for infection from Gram-negative organisms such as Pseudomonas aeruginosa and Klebsiella pneumonia, which require aggressive therapy. Powerful antibiotics used against these organisms include the fourth-generation cephalosporins, carbapenems, or ciprofloxacin alone or in combination with an aminoglycoside (entamicin or tobramycin). A pilot study of inhaled (aerosol) tobramycin showed the novel form of this aminoglycoside to be as effective against P. aeruginosa as its intravenous formulation. Multidrug therapy may be necessary, particularly for patients on mechanical ventilators, who are at very high risk for multiple dangerous organisms. A 2006 study of high-dose ampicillin-sulbactam for multidrug-resistant (MDR) Acinetobacter baumannii pneumonia showed the combination to be 66.7 - 77.8% successful in curing critically ill, ventilator-dependent patients of the bacterial infection.
Antibiotics for P. Jiroveci Pneumonia (Common in HIV-Positive Patients)
Trimethoprim-sulfamethoxazole is the first choice for both preventing and treating P. Jiroveci (formerly called P. carinii) pneumonia in HIV-positive patients. Clindamycin-primaquine may be used in patients who do not respond to standard therapies.
A study of children with leukemia found atovaquone to be an excellent alternative for preventing P. jiroveci pneumonia in children who cannot tolerate trimethoprim-sulfamethoxazole, the current standard preventing therapy.
Side Effects of Antibiotics
Most antibiotics have the following side effects (although specific antibiotics may have other side effects or fewer of the standard ones).
- The most common side effect for nearly all antibiotics is stomach problems.
- Antibiotics raise the risk of vaginal infections. Taking acidophilus supplements or eating yogurt with active acidophilius cultures may help restore healthy bacteria that offset the risk for such infections.
- Overuse of antibiotics can cause infection with Clostridium difficile, a pathogen responsible for causing severe diarrhea, colitis, and abdominal pain. It can be fatal.
- Allergic reactions can occur with all antibiotics, but are most common with medications derived from penicillin or sulfa. These reactions can range from mild skin rashes to rare but severe -- even life-threatening -- anaphylactic shock.
- Certain drugs, including some over-the-counter (OTC) medications, interact with antibiotics. Patients should inform the physician of all medications and OTC preparations they are taking and of any drug allergies they might have.
Antibiotic Classes
Beta-Lactams
Beta-lactam antibiotics share common chemical features. They include penicillins, cephalosporins, and some newer similar agents. They interfere with bacterial cell walls.
Penicillins. Penicillin was the first antibiotic. There are many forms to this still-important agent:
- Natural penicillins include penicillin G (for intravenous use) and V (for oral use).
- Penicillin derivatives called aminopenicillins, particularly amoxicillin (Amoxil, Polymox, Trimox, Wymox, or any generic formulation), are now the most common penicillins used. Amoxicillin is inexpensive and, at one time, was highly effective against S. pneumoniae. Unfortunately, bacterial resistance to amoxicillin has increased significantly, both among S. pneumoniae and H. influenzae. Ampicillin is similar and is an alternative to amoxicillin, but requires more doses and has more severe gastrointestinal side effects.
- Amoxicillin-clavulanate (Augmentin) is an augmented penicillin that works against a wide spectrum of bacteria. An extended release form has been approved for treating adults with community-acquired pneumonia caused by bacterial strains that have become resistant to penicillin.
- Antistaphylococcal penicillins were developed to treat Staphylococcus aureus. The standard drug was methicillin, but it is no longer used routinely due to very high rates of resistance in hospital-acquired pneumonias. Resistance in community-acquired Staphylococcus aureus is also increasing. Alternatives include vancomycin and linezolid.
- Certain penicillins used against Pseudomonas aeruginosa include ticarcillin and piperacillin. Piperacillin is more effective that ticarcillin.
Many people have a history of an allergic reaction to penicillin, but research suggests that the allergy may not recur in a significant number of adults. Skin tests are available to help determine if those with a history of penicillin allergies could use these important antibiotics.
Cephalosporins. Most of these agents are not very effective against bacteria that have developed resistance to penicillin. They are classed according to their generation:
- First generation includes cephalexin (Keflex), cefadroxil (Duricef, Ultracef), and cephradine (Velosef).
- Second generation includes cefaclor (Ceclor), cefuroxime (Ceftin), cefprozil (Cefzil), and loracarbef (Lorabid),
- Third generation includes cefpodoxime (Vantin), cefdinir (Omnicef) cefditoren (Sprectracef), cefixime (Suprax), and ceftibuten (Cedex). Ceftriaxone (Rocephin) is an injected cephalosporin. These are effective against a wide range of Gram-negative bacteria. Cefditoren has also been shown to be 85% effective against Haemophilus influenzae and 90% effective against penicillin-resistant strains of S. pneumoniae.
Other Beta-Lactam Agents. Carbapenems include meropenem (Merrem), biapenem, faropenem, ertapenem (Invanz) and combinations (imipenem/cilastatin [Primaxin]). These agents cover a wide spectrum of bacteria. They are now used for serious hospital-acquired infection and for bacteria that have become resistant to other beta-lactams. Imipenem has serious side effects when used alone, so it is given in combination with cilastatin to offset these adverse effects. The newer agents are less toxic, although they may not be as potent.
Sanfetrinem, a novel beta-lactam antibiotic known as a trinem is proving to be effective against S. pneumoniae,H. influenzae, and M. catarrhalis.
Ceftobiprole is an investigational beta-lactam in phase III clinical trials for methicillin-resistant Staphylococcus aureus (MRSA), penicillin-resistant streptococci, and other Gram-negative pathogens. Other anti-MRSA beta-lactams in clinical development include CS-023/RO-4908463, a carbapenem, and ceftaroline, a cephalosporin (PPI-0903).
Fluoroquinolones
Fluoroquinolones (quinolones) interfere with the bacteria's genetic material to prevent reproduction.
- Ciprofloxacin (Cipro), a second-generation quinolone, remains the most potent quinolone against Pseudomonas aeruginosa. It is not very effective for Gram-positive bacteria such as Streptococcus pneumoniae.
- "Respiratory" quinolones are currently the most effective drugs available for a wide range of bacteria. Such drugs include levofloxacin (Levaquin), sparfloxacin (Zagam), and gemifloxacin (Factive). Some of the newer fluoroquinolones only need to be taken once a day.
- The fourth generation quinolones Moxifloxacin (Avelox) and clinafloxacin, which is still under development, are proving to be effective against anaerobic bacteria.
S. pneumoniae -- strains resistant to the "respiratory" quinolones are uncommon in the U.S., but resistance is dramatically increasing.
Many quinolones cause side effects, including sensitivity to light and neurologic, psychiatric, and heart problems. Pregnant women should not take these agents. The drugs also enhance the potency of oral anti-clotting agents.
Macrolides, Azalides, and Ketolides
Macrolides and azalides also affect the genetics of bacteria. They include:
- Erythromycin
- Azithromycin (Zithromax, Zmax)
- Clarithromycin (Biaxin)
- Roxithromycin (Rulid)
These antibiotics are effective against atypical bacteria such as mycoplasma and chlamydia. They are also used in some cases for S. pneumoniae and M. catarrhalis, but there is increasing bacterial resistance to these agents. All but erythromycin are effective against H. influenzae. Macrolide-resistance rates doubled between 1995 and 1999 as more and more children were being treated with these antibiotics. Some research suggests these agents may reduce the risk of a first heart attack in some patients by reducing inflammation in the blood vessels.
Extended-release (ER) azithromycin (Zmax) is the first anti-pneumonia antibiotic that can be given in a single dose. It is effective against Gram-positive, Gram-negative, and atypical pathogens. Studies have shown the results to be equal (noninferior) to that acheived with 7 days of levofloxacin or clarithromycin ER in patients wtih CAP. A single-dose antibiotic decreases the likelihood that a patient will discontinue taking the antibiotic early, which rapidly contributes to the development of drug-resistant bacteria.
Ketolides. Ketolides are a new class of antibiotic drugs. They are derived from erythromycin and were developed to combat organisms that have become resistant to macrolides. Telithromycin (Ketek), the first antibiotic in the ketolide class, was approved by the FDA in 2004 for treatment of community-acquired pneumonia (CAP).
In February 2007, the FDA withdrew approval of Ketek for treatment of acute bacterial sinusitis. The agency decided that the serious risks of telithromycin outweigh its benefits for sinusitis treatment. The decision followed several 2006 reports of patient deaths due to severe liver damage. Telithromycin is approved for treatment only of CAP. The drug carries a black box warning noting the potentially serious side effects, including liver failure, vision problems, loss of consciousness, and neuromuscular problems.
Tetracyclines
Tetracyclines inhibit bacterial growth. They include doxycycline, tetracycline, and minocycline. They can be effective against S. pneumoniae and M. catarrhalis, but bacteria that are resistant to penicillin are also often resistant to doxycycline. The side effects of tetracyclines include skin reactions to sunlight, burning in the throat, and tooth discoloration.
Aminoglycosides
Aminoglycosides (gentamicin, kanamycin, tobramycin, amikacin) are given by injection for very serious bacterial infections. They can be given only in combination with other antibiotics. Some are available in inhaled forms or by applying a solution directly to mucous membranes, skin, or body cavities. They can have very serious side effects, including hearing damage, balance problems, and kidney damage.
Lincosamide
Lincosamides prevent bacteria from reproducing. The most common lincosamide is clindamycin (Cleocin). This antibiotic is useful against S. pneumoniae and S. aureus, but not against H. influenzae.
Glycopeptides
Glycopeptides (vancomycin, teicoplanin) are used for Staphylococcus aureus infections that have become resistant to standard antibiotics. The drug can be taken by mouth or given intravenously. The latest generation of glycopeptides, a derivative of vancomycin, is called telavancin. Currently in phase III studies of hospital-acquired pneumonia, it looks positive for the treatment of Gram-positive pneumonia.
Trimethoprim-Sulfamethoxazole
Trimethoprim-sulfamethoxazole (Bactrim, Cotrim, Septra) is less expensive than amoxicillin. It is particularly useful for adults with mild bacterial upper respiratory infections who are allergic to penicillin. The drug is no longer effective against certain streptococcal strains. It should not be used in patients whose infections occur after dental work, or in people allergic to sulfa drugs. Allergic reactions can be very serious.
Oxazolidinone
Linezolid (Zyvox) is the first antibacterial drug in a new class of synthetic antibiotics called oxazolidinones. It has been shown to work against certain aerobic Gram-positive bacteria.
Other Agents
Inhaled polymyxin, a drug used in cystic fibrosis patients, is showing efficacy against pneumonia caused by multidrug-resistant Gram-negative bacteria, including pseudomonas and klebsiella.
Preventing and Treating Respiratory Syncytial Virus (RSV) Pneumonia in Children
Prevention of RSV. Two agents have been approved for protecting high-risk infants against RSV pneumonia:
- Palivizumab (Synagis) is known as a monoclonal antibody, a genetically engineered antibody that targets the RSV virus. It is given by an injection into the muscle. Early studies of motavizumab, another monoclonal antibody in development, also show potent protection against RSV.
- RSV immune globulin (RespiGam) is made up of antibodies to RSV that are obtained from the blood of healthy infants. RespiGam is given as a shot.
Treatment of RSV. Ribavirin is the first treatment approved for RSV pneumonia, although it has only modest benefits. The American Academy of Pediatrics recommends it for children at high risk for serious complications of RSV. In one study, a combination of ribavirin with RSV immune globulin was more effective than either drug used alone.
Drugs called bronchodilators, which open up the airways, are sometimes used to treat RSV infection. However, evidence is conflicting. One study involving albuterol, a common bronchodilator, found that epinephrine may be more effective.
Surgery
Although most patients with pneumonia do not require invasive therapy, it may be necessary in patients with abscesses, empyema, or certain other complications.
Thoracotomy
Thoracotomy is the standard surgery for pneumonia. It requires general anesthesia and an incision to open the chest and view the lungs. This procedure allows the surgeon to remove dead or damaged lung tissue. In severe cases, the entire lobe of the lung is removed. This is calledalobectomy. Remaining healthy lung tissue re-expands after surgery to make up for tissue that has been removed.
Chest Tubes
Chest tubes are used to drain infected pleural fluid. Tubes are not typically required for pneumonia or abscesses. The tubes are inserted after the patient is given a local anesthetic. They remain in place for 2 - 4 days, and are removed in one quick movement. This can be very distressing, although some patients experience no discomfort. Complications of chest tubes include infection, accidental injury of the lung, perforation of the diaphragm, and fluid build-up within the lung if the pleural fluid is removed too rapidly. Removing the chest tubes may cause the lung to collapse, requiring the reintroduction of a chest tube to inflate the lung.
Click the icon to see an illustrated series detailing chest tube insertion.
Prevention
The best way to prevent serious respiratory infections such as pneumonia is to avoid those who are sick (if possible), and to practice good hygiene. [See In-Depth Report #94: Colds and influenza.]
Good Hygiene and Preventing Transmission
Colds and flu are spread primarily from infected persons who cough or sneeze. A very common method for transmitting a cold is by shaking hands. Hands should always be washed before eating and after going outside. Using ordinary soap is sufficient. Alcohol-based gels are also effective for every day use, and may even kill cold viruses. If extreme hygiene is required, alcohol-based rinses are needed.
Antibacterial soaps add little protection, particularly against viruses. In fact, one study suggests that common liquid dish washing soaps are up to 100 times more effective than antibacterial soaps in killing respiratory syncytial virus (RSV). Wiping surfaces with a solution that contains one part bleach to 10 parts water is very effective in killing viruses.
Changing Hospital Practices
Bacteria abound in hospitals and long-term care facilities, and are particularly virulent in areas with the sickest patients, such as intensive care units. Health care facilities are revising many of their practices and educating physicians, nurses, and therapists how to reduce the likelihood of transmitting bacteria.
- A Swiss study found that coating endotracheal tubes with a solution of silver chloride and silver salts inhibited the growth of bacteria and reduced the transmission of Pseudomonas aeruginosa.
- Another more widely adopted method involves the daily use of oral antibiotics to clean the mouths of patients on ventilators. This practice has been shown to lower the incidence of ventilator-associated pneumonia.
Dietary Factors
Foods Containing Lactobacilli (Good Bacteria). Friendly bacteria inside the intestines may help keep you healthy. Researchers are studying the possible protective value of certain strains of lactobacilli bacteria found in the intestines. One such strain is acidophilus, which is used to make yogurt. According to a Finnish study, children attending day care who drank milk containing the strain lactobacilli GG reduced their risk of respiratory infections by 10 - 20%. More research is needed. (The strain used in the Finnish study was not the kind found in most commercial yogurt products.)
Vitamins. Studies are mixed when it comes to whether or not vitamin supplements protect against upper respiratory infections. Large doses of vitamin C, for example, may help reduce the duration of a cold, but they do not appear to protect against one in the first place. Two studies in 2002 on multivitamins reported opposite results, with one finding fewer infections and one finding no difference. It is possible that vitamin C or multivitamin supplements may be helpful in specific people, such those who are vitamin deficient or have medical problems that impair their immune systems.
Medications
A review of more than 134,000 Swiss patients found that use of cholesterol-lowering statin drugs was associated with a significantly lower risk of fatal pneumonia and a somewhat lower risk of less-severe pneumonia.
Factors That Lower The Risk for Respiratory Infections
Breast-feeding. Some evidence suggests that women who breast-feed reduce the risk of respiratory infections in their children.
Low Stress and Active Social Life. Several studies have reported that socially active people with low stress have fewer colds than people who have high stress levels or those who have low stress and few social connections.
Zinc
Zinc appears to have certain important effects on the immune system, and it may have a direct effect on viruses. Zinc preparations in lozenge or nasal gel form are now available as cold treatments. However, research findings regarding the benefits of zinc have varied. (The differing results may be due to different zinc preparations.)
- A nasal gel containomg zinc gluconate has shown some success, possibly because the gel sticks to the nasal passages long enough for the zinc to interact with the virus. In a 2003 study, patients who took the nasal gel within 14 - 48 hours of getting sick had less severe symptoms and felt better faster than those who took a placebo. The finding supports earlier studies reporting that Zicam shortened the duration of a cold by about two days.
- Zinc lozenges are showing mixed results. One 2000 study suggested that the use of zinc acetate lozenges (e.g., Fast-Dry, Galzin) may be more effective and have a better taste than other formulations, such as zinc gluconate (Cold-Eeze, Orazinc). On the other hand, a 2002 study reported that zinc gluconate reduced the duration of colds significantly. To further confuse matters, the two zinc lozenge preparations were directly compared in a 2000 study, and neither was effective. The reasons for these conflicting results are not clear.
- A small 2001 study on a nasal spray preparation found no benefits. The spray preparation had less zinc than the nasal gel.
In any case, no one with an adequate diet and a healthy immune system should take zinc for prolonged periods for preventing colds.
Side Effects of Zinc. Side effects include:
- Dry mouth
- Constipation
- Nausea
- Bad taste (possibly only with zinc gluconate lozenges)
- Overdose may cause severe vomiting, dehydration, and restlessness. Call a physician if any of these symptoms occur.
- In rare cases, an allergic response may occur.
Food and Drug Interactions. Zinc may also interact with drugs or other elements.
- It may reduce absorption of certain antibiotics.
- Foods high in calcium or phosphorus may reduce zinc absorption.
- Used in high doses for long periods of time, zinc can cause copper deficiencies.
Herbs and Supplements
Herbal remedies and dietary supplements are not regulated by the FDA. This means that manufacturers and distributors do not need FDA approval to sell their products. In addition, any substance that affects the body's chemistry can, like any drug, produce side effects that may be harmful. There have been a number of reported cases of serious and even deadly side effects from herbal products.
The following are special concerns for people taking natural remedies for colds:
- Echinacea. The herbal remedy echinacea is commonly taken to prevent onset and ease symptoms of cold or flu. Studies have been mixed on its effectiveness. It is difficult to test, however, since it is available in different species (notably, E. purpurea and E. augustifolia ), and preparations vary from using extracts to dried forms of the root, the herb, or the whole plant. If echinacea is helpful at all, it may be more effective taken before symptoms develop than during the cold or flu. However, evidence suggests that it is not helpful at all. In addition, allergic reactions have been reported. People with autoimmune diseases or who have plant allergies should avoid taking it. There have also been some reports of a reaction called erythema nodosum associated with echinacea. This involves a rash, sometimes accompanied by fever, headache, muscle and joint aches, and sore throat.
- Grapeseed extract is sometimes touted as a natural antihistamine. A 2002 study, however, reported no benefits from it.
- Chinese herbal cold and allergy medications may contain trace amounts of aristolochic acid, a chemical that is toxic to the kidneys and considered a carcinogen. Products containing aristolochic acid have been associated with several reports of kidney failure in Europe. Of specific concern are studies suggesting that up to 30% of herbal patent remedies imported from China having been laced with potent pharmaceuticals such as phenacetin and steroids. Most reported problems occur in herbal remedies imported from Asia, with one study reporting a significant percentage of such remedies containing toxic metals.
Anti-Viral Drugs: Neuraminidase Inhibitors
Brands and Benefits. Zanamivir (Relenza) and oseltamivir (Tamiflu) are called neuraminidase inhibitors. They are newer agents that have been designed to block a key viral enzyme called neuraminidase, which helps viruses spread (replicate).
Both zanamivir and oseltamivir have the following benefits:
- Neuraminidase inhibitors are effective for treating both A and B strains of influenza. M2 inhibitors, which prevent the virus from reproducing, are only effective against type A.
- They shorten the duration of the flu by 1 - 3 days.
- They may help reduce transmission of the virus, although evidence is needed to confirm these findings.
- They may have a lower risk than M2 inhibitors for emerging viral strains that are resistant to their effects. In January 2006, the Centers for Disease Control and Prevention (CDC) released a Heath Alert (the highest level of importance) regarding the use of M2 inhibitors (amantadine and rimantadine) for the prevention or treatment of flu. Due to significant increase in influenza A resistance to this class of antiviral medication, the CDC recommended against its use for the remainder of the 2005 - 2006 flu season.
- Oseltamivir has been shown to prevent influenza from progressing to pneumonia in 50% of children who were given the drug within 1 day of being diagnosed with the flu.
- They have fewer serious side effects than the M2 inhibitors.
- Both have some benefits for preventing influenza. Only oseltamivir has been approved for this purpose, however, and only in people over age 13.
Limitations and Side Effects. Although they have many advantages compared to the M2 inhibitors, they are much more expensive. They also need to be taken within 2 days of symptoms to be effective. There are also some differences between the two agents that could be significant for some individuals:
- Zanamivir (Relenza) is administered as a nasal spray or inhaler. People with asthma or other lung disorders may experience airway spasms and should use this drug with caution. Side effects are minor in most patients. Of concern, however, was a 2001 British study, which found that a majority of elderly patients were not able to properly use the zanamivir (Relenza) inhaler device, rendering the medicine virtually ineffective. The study was small, however, and other reports suggest that zanamivir is sill effective in this older group.
- Oseltamivir comes in capsule and liquid form. Side effects are also minor, but about 10 - 15% of patients experience nausea and vomiting. Patients with kidney dysfunction should take lower doses.
Antiviral Drugs for Prevention of The Flu
To date both M2 inhibitors and oseltamivir have been approved for prevention of influenza.
- M2 inhibitors. Amantadine and rimantadine protect against the influenza A infection itself in about half of individuals. Rimantadine is preferred for prevention during outbreaks of influenza A because it has fewer adverse side effects. Unfortunately, a majority of influenza A strains are now resistant to both M2 inhibitors.
- Neuraminidase Inhibitors. Both zanamivir (Relenza) and oseltamivir (Tamiflu) help prevent both influenza A and B. Only oseltamivir has been approved for this purpose, however, and only in people over 13. Both appear to be very effective in preventing influenza in people who have been exposed to family members with the flu.
Antiviral drugs are not a substitute for vaccines, but they are extremely important add-on therapy for people in certain high-risk groups. They may also be used:
- In combination with the flu vaccine during seasons where there is a poor match between the virus and vaccine.
- In high-risk individuals who are vaccinated after the flu season has started. In such cases, it takes about 2 weeks (or longer in children) for the vaccine to take effect. The anti-viral drugs offer protection during that period.
- As supplementary protection for vaccinated people in high-risk groups, such as the elderly or people with compromised immune systems.
- In people who cannot have vaccinations for whatever reason.
- For people who provide care for high-risk individuals.
- For high-risk individuals who cannot or will not be vaccinated.
Viral Influenza Vaccines (Flu Shot)
Description of Vaccines. Vaccines against the flu (or a "flu shot") use inactivated (not live) viruses. They are designed to provoke the immune system to attack antigens contained on the surface of the virus. Antigens are foreign molecules that the immune system specifically recognizes and targets for attack.
Unfortunately, the antigens in these influenza viruses undergo genetic alterations (called antigenic drift) over time, so they are likely to become resistant to a vaccine that worked in the previous year. Vaccines must be redesigned annually to match the current strain.
- Influenza A. The influenza A virus is further categorized by primary molecular antigens (hemagglutinin and neuraminidase), which serve as the targets for the vaccines. Influenza A is a particular problem because it can infect other species, such as pigs or chickens, and undergo major genetic changes.
- Influenza B viruses tend to be more stable than influenza A viruses, but they too vary. Although influenza B has been far less common than A, a vaccine for type B is important because experts are concerned that small children who have not developed immunity to the virus will experience severe flu if they are exposed to type B.
A live but weakened intranasal vaccine (FluMist) for healthy people aged 5 - 49 years is approved by the FDA. It is known as a live, attenuated, trivalent, intranasal influenza vaccine (LAIV). The vaccine is engineered to grow only in the cooler temperatures of the nasal passages, not in the warmer lungs and lower airways. It boosts the specific immune factors in the mucous membranes of the nose that fight off the actual viral infections. FluMist is a nasal spray. In one study it protected up to 93% of children against the flu.
Timing and Effectiveness of the Vaccine. Ideally, people should get a flu shot every October or November. However, it may take longer for a full supply of the vaccine to reach certain locations. In such cases, the high-risk groups should be served first.
Antibodies to the influenza virus usually develop within 2 weeks of vaccination. Immunity peaks within 4 - 6 weeks, then gradually wears off. That is why most people should get a flu shot every year.
In healthy adults, the flu shot reduces the chance of illness by 70 - 90%. The current flu vaccines may be slightly less effective in the elderly and those with certain chronic diseases. Even in people with weak immune systems, however, the vaccine usually protects against serious flu complications, particularly pneumonia. In fact, among the elderly, interesting studies are now suggesting that influenza vaccination may help protect against stroke, adverse heart events, and death from all causes.
Children Who Should Be Vaccinated.The American Academy of Pediatrics (AAP) and the CDC recommend flu shots for all healthy children 6 - 23 months of age. The flu shot is not approved for children less than 6 months of age.
In addition, any child over the age of 2 years who has a condition that requires regular medical care or who has been hospitalized for a serious illness (particularly lung or kidney disease, diabetes, sickle cell anemia, or immune deficiencies) should also receive a flu shot. Children who are receiving long-term aspirin therapy should also be immunized against the flu, because they are at higher risk for Reye syndrome, a life-threatening disease, if they get the flu.
Children with Asthma. Recent and major studies have found that the flu shot is safe for children with asthma. It is very important for these patients to reduce their risk for respiratory diseases. Unfortunately, 90% of asthma patients remain unvaccinated.
Older Children and Adults Who Should Be Vaccinated. The following, in order of priority, are the population groups who should be vaccinated each year. The first two groups have the highest need for influenza vaccinations and are given top priority:
- All adults age 65 and older. Older adults who receive a flu shot have lower hospitalization r