Encephalitis: Viral

Description

Vaccinations

Measles used to be a very common childhood disease and is usually self-limited. In severe cases, however, measles can cause pneumonia and in about one out of 1,000 cases it can lead to encephalitis or death. The risk for these severe complications is highest in the very young and very old. In pregnant women, measles increases the rates for miscarriage and low birth weight and birth defects in their infants. Aggressive vaccination programs have reduced the incidence of measles in the US to fewer than 100 cases a year. About one-third were imported from other countries. Full-blown measles cases among unvaccinated children still remains a serious international problem, with 42 million cases and 800,000 deaths in small children each year. In very rare cases, encephalopathy (brain damage) associated with the live-measles vaccine has occurred, but the risk is far lower than brain events from the disease itself.

Vaccine for Varicella Virus (Chicken Pox and Herpes Zoster)

Herpes zoster, or shingles, is a reactivation of the virus that causes chicken pox (varicella virus). A live-virus vaccine (Varivax) produces persistent immunity against chicken pox. Data show that the vaccine can prevent chicken pox or reduce the severity of the illness even if it is used within three days, and possibly up to five days, after exposure to the infection. The vaccine is protective in about 85% of cases, and even if a vaccinated person becomes infected, the disease is almost always mild. In spite of some concerns, studies are also finding that protection is long lasting. The vaccine is now recommended for all children between the ages of 18 months and adolescence who have not yet had chicken pox. (In spite of these recommendations, the vaccine is still not being as widely administered as other vaccinations.)

Vaccine against Flaviviruses (West Nile Virus, Japanese Encephalitis Virus, St. Louis Encephalitis)

Researchers are investigating a number of vaccines against the flaviviruses.

A vaccine (Je-Vax) is currently available for Japanese encephalitis. In travelers, it is only recommended for those visiting rural areas in high-risk Asian countries for more than 30 days. These countries include China, Korea, India and neighboring areas, and Southeast Asia. The disease may occur with lower frequency in Japan, Taiwan, Singapore, Hong Kong, and eastern Russia.

Vaccines are also under investigation for West Nile virus, but any human application is years away. Some evidence suggests that the vaccine against Japanese encephalitis may also reduce the severity of West Nile virus.

Rabies Vaccine

Anyone who is exposed to bats, or is exposed to secretions of an animal suspected of having rabies, should be given the rabies vaccine, whether or not there are indications of rabies. Exposed individuals should also receive immune globulin unless they were previously vaccinated. Veterinarians and animal handlers should be vaccinated. This does not eliminate the need for treatment if they are exposed to rabies, but it reduces the intensity of the treatment. Side effects include:

• Pain.
• Redness.
• Headache.
• Stomach pain.
• Nausea.
• Dizziness.
• Muscle aches.
• Swelling at the injection site.

Allergic response can occur after the first shot and as long as 21 days after a booster shot. Rare cases of neurological disorders have been reported that cause pain and paralysis in the legs and arms, which clear up in about 12 weeks.