Diagnosis
Differentiating between a cold and flu is often one of degree and may be difficult. Cold symptoms are nearly always milder than those of the flu.
Comparing Colds and Flus
Symptoms
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Cold
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Flu
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Fever
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Rare.
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Common and high (102-104 degrees F); lasts 3-4 days.
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Headache
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Rare.
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Almost always present.
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General aches and pains
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Mild, if they occur at all.
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Often severe.
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Fatigue, exhaustion, and weakness
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Mild, it they occur at all.
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Extreme exhaustion is early and severe. Fatigue and weakness can last two to three weeks.
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Stuffy nose
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Nearly always.
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Sometimes.
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Sneezing
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Very common.
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Sometimes.
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Sore throat
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Common.
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Sometimes.
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Chest discomfort and cough
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Mild to moderate, hacking cough.
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Common, can be severe.
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From National Institute of Allergy and Infectious Disease.
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Diagnostic Tests for Influenza
A number of tests are available to isolate and identify viruses responsible for some respiratory infections. They are generally not needed, since most cases of influenza are self-evident, but they can be very helpful in confirming or ruling out influenza. If a physician believes a diagnosis would help, samples using a swab should be obtained from the nasal passages or throat within four days of the first symptoms.
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| A nasopharyngeal culture is a test used to identify organisms that can be in nasal secretions causing disease. Nasopharyngeal cultures are useful in identifying Bordetella pertussis and Neisseria meningitidis (types of bacteria). The culture may be used to test for appropriate antibiotic therapy. |
A number of rapid tests for influenza are available that can produce results in less than 30 minutes, but vary on the specific strain or strains that they can detect. They are not as accurate as a viral culture, however, in which the virus is reproduced in the laboratory; culture results can take 3 to 10 days. Blood tests can also document the infection several weeks after symptoms appear.
Ruling out Other Causes of Congestion
Ruling out Allergic Rhinitis. Symptoms of allergic rhinitis include nasal obstruction and congestion, which are similar to the symptoms of a cold. People with allergies, however, are apt to have the following:
- Thin, clear, and runny nasal discharge.
- An itchy nose, eyes, or throat.
- Recurrent sneezing.
There are two forms of allergic rhinitis:
- Symptoms that appear only during allergy season (spring or fall) are called seasonal rhinitis (commonly known as hay or rose fever).
- Allergens in the house, such as house dust mites, molds, and pet dander, can cause year-long allergic rhinitis, referred to as perennial rhinitis.
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Click the icon to see an image of common allergens. |
Ruling out Sinusitis. The signs and symptoms suggestive of true acute sinusitis include the following:
- A return of congestion and discomfort after initial improvement in a cold (called double sickening).
- Purulent (pus-filled) nasal secretion.
- A lack of response to decongestant or antihistamine.
- Pain in the upper teeth or pain on one side of the head.
- On leaning forward, facial pain above or below both eyes.
Children with sinusitis are less likely to have facial pain and headache and may only develop a high fever or prolonged upper respiratory symptoms (e.g., a daytime cough that does not improve for 11 to 14 days). When the diagnosis is unclear or complications are suspected, further tests may be required.
Ruling Out Other Causes of Coughing
Acute Bronchitis. Acute bronchitis is usually caused by a virus and in most cases is self-limiting. The cough it causes typically lasts for about a week to ten days, but in about half of patients, coughing can last for up to three weeks, and 25% of patients continue to cough for over one month.
Atypical Pneumonia. Pneumonia caused by atypical organisms (e.g., Mycoplasma pneumonia, Legionella) can have very similar symptoms and only laboratory tests can rule them out, if they are suspected.
Ruling out More Serious Viral Infections. Respiratory syncytial virus (RSV) and, possibly human parainfluenza viruses (HPV), are proving to be important causes of serious respiratory infections in infants, the elderly, and people with damaged immune systems. (Both also cause mild conditions.) RSV may be a much more common cause of flu-like symptoms than previously thought. In one British study of patients with flu symptoms, RSV was responsible for 22% of the cases and influenza for 32%. And among children under five, RSV was responsible for more flu-like cases than the influenza virus itself.
Pertussis. Pertussis (whooping cough) was a very common childhood illness throughout the first half of the century. The disease is very easily spread from one person to another. Although immunizations caused a decline in cases to only 1,700 in the U.S. in 1980, the incidence has risen recently, with almost 30,000 cases reported between 1997 and 2000 (17 infants died of the disease in 2000). Many more cases are reported worldwide. Nearly half of pertussis cases now occur in people 10 years of age or older, perhaps due to waning immunity in adolescents and adults. Such cases may be greatly underreported. One study suggested that as many as 25% of adults who see a doctor for persistent cough may actually have pertussis. It may go undiagnosed, however, because symptoms are usually mild and adults are unlikely to have the classic whooping cough. This is of some concern because such adults may unknowingly infect unvaccinated children. The younger the patient, the higher the risk for severe complications, including pneumonia, seizures, and even death. Children younger than six months are at particular risk because even with vaccination, protection is incomplete.
Ruling Out Other Causes of Sore Throat
In addition to common cold viruses, other, less frequent causes of sore throat include the following:
- Strep throat.
- Sore throat related to influenza.
- Foodborne and waterborne infections (Streptococcus C and G). These agents mimic strep throat but are usually less severe and do not cause rheumatic fever.
- Sore throat and tonsillitis caused by an uncommon organism called Arcanobacterium haemolyticum. An infection with this bacterium can mimic strep throat and may even cause a rash. It should be suspected in patients with symptoms that suggest strep but there is no laboratory evidence of strep. It can be treated with erythromycin.
- Infectious mononucleosis ("mono"). Mononucleosis is caused by the Epstein-Barr virus. It usually occurs in adolescents and young adults. Sore throat is accompanied by chills, fever, swollen glands, and fatigue. Treatment involves avoiding vigorous activities for the first one or two months and managing symptoms.
- Herpesvirus. The herpesvirus 1 may cause severe sore throat, most often in college students.
- Pneumonias caused by the atypical organisms Mycoplasma or Chlamydia. These forms of pneumonia typically occur in young adults and may cause sore throat as well as fever and cough.
What is Strep Throat?
Group A Streptococcal bacteria is the most common bacterial cause of the severe sore throat known commonly as "strep throat." It occurs mostly in school age children, but people of all ages are susceptible. (Strep throat constitutes only about 12% of all sore throat cases seen by doctors.)
The symptoms of strep throat include the following:
- A sudden onset of severe sore throat.
- Difficulty in swallowing.
- Fever.
- The patient may also have a headache, stomach pain, and vomiting.
Only about half of patients with strep throat have such clear-cut symptoms, however. Furthermore, half of people who have these symptoms do not actually have strep throat.
How Is Strep Throat Diagnosed?
Most cold-related sore throats are caused by viruses and require no treatment. They usually do not last more than a day. When the sore throat persists and is very painful the physician will want to rule out or confirm the presence of group A Streptococcal bacteria, the cause of strep throat, which can be treated with antibiotics.
The physician will take the following steps when strep throat is suspected:
- Look for redness and pus-filled patches on the tonsils and back of the throat. (Enlarged tonsils are less likely to indicate a strep throat.)
- Feel the sides of the neck for swollen lymph nodes. (If the lymph nodes are not swollen, it is less likely to be a strep throat.)
- Use a cotton swab to take a sample of pus in the throat for a throat culture.
Throat Culture. A culture taken from the throat sample is the most effective and least expensive test for confirming the presence of the Streptococcal bacteria.
- The sample is sent to a laboratory, where it is cultured; that is, the sample is added to special substances so that any bacteria present will reproduce.
- It takes between 24 hours and 48 hours to obtain a result.
Rapid Antigen-Detection Test for Strep Throat. A faster test called the rapid strep antigen test uses chemicals to detect the presence of bacteria in a few minutes. A positive result nearly always means that Streptococcal bacteria is the cause of the infection. The test, however, fails to detect between 10% and 20% of cases, and so a culture may still be necessary to catch any missed infections, particularly in children.
How Serious is Strep Throat?
The use of antibiotics has removed the threat of most complications from streptococcus infection in the throat (strep throat). However, untreated strep throat could lead to the following complications:
- Abscess in the tonsils.
- Scarlet fever.
- Rheumatic fever. This condition, although very rare in the U.S., can injure the heart and have long term serious effects.
How Is Strep Throat Treated?
Throat infections caused by group A Streptococcal bacteria (strep throat) require antibiotics. The following are generally used:
- Penicillin is usually the antibiotic of choice unless the patient is allergic. A full 10 days may be necessary. Amoxicillin, a form of penicillin, is proving to be effective when taken in a single daily dose for 10 days.
- Macrolide antibiotics. Erythromycin is known as a macrolide antibiotic and is the first choice for patients with penicillin allergies. A 10-day regimen is needed. Another macrolide, azithromycin, can be given as a single daily dose and may be effective in five days. It is expensive, however, and bacterial resistance to macrolides is growing, so it should not be given as a first choice.
- Cephalosporins are a potent, but expensive, group of antibiotics that are very effective in eradicating the bacteria.
Antibiotics are very commonly inappropriately prescribed for non-Strep sore throats. One study reported that estimated 6.7 million American adults visited their physicians because of sore throat between 1989 and 1999. And, 73% of them were given antibiotics. Studies indicate, however, that less than half of adults and far fewer children with even strong signs and symptoms for strep throat actually have Streptococcal infections.
Parents should be comforted that a delay in antibiotic treatment while waiting for lab results does not increase the risk that the child will develop serious long-term complications, including acute rheumatic fever. If a patient is severely ill, however, it is reasonable to begin administering antibiotics before the results are back. If the culture is negative (there is no evidence of bacteria), then the physician should call the family to make certain they stop taking the antibiotics and discard any remaining pills.
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