Encephalitis is an inflammation caused by a viral infection. The specific viruses involved may vary and although exposure to viruses can occur through insect bites, food or drink, or skin contact, travelers are most at risk to exposure from insect bites. In rural areas, arboviruses that are carried by mosquitoes or ticks are the most common cause of infection.
While there have been outbreaks in recent years in the United States of several forms of encephalitis, such as West Nile encephalitis and St. Louis encephalitis, travelers abroad are most at risk for Japanese encephalitis and tickborne encephalitis.
Japanese encephalitis is a mosquito-borne viral disease that occurs mainly in:
- China, Japan, and Korea
- Eastern Russia
Japanese encephalitis also occurs at a lower frequency in Taiwan, Singapore, and Hong Kong. In all of these areas, Japanese encephalitis is primarily a rural disease.
Occurrence of the disease is quite low. On average, among persons who are infected by a mosquito bite, only a very few will develop an illness. While the majority of persons who are infected develop only mild or no symptoms, among those who develop encephalitis, the consequences are grave.
A vaccine for Japanese encephalitis is currently available in the United States through most travelers' clinics. The Centers for Disease Control and Prevention (CDC) generally recommends the vaccine only for persons who will travel in rural areas for four weeks or more, except for circumstances where there is a known outbreak of Japanese encephalitis.
In addition, travelers should take precautions to prevent insect bites, including the following:
- Minimize outdoor exposure during the cooler hours at dusk and dawn, when mosquitoes that transmit the disease feed.
- Wear mosquito repellents containing DEET as an active ingredient.
- Stay in air conditioned or well-screened rooms.
In addition, travelers to rural areas should bring a portable bednet and apply permethrin, a mosquito repellent/insecticide to clothing.
Tickborne encephalitis is a viral infection of the central nervous system transmitted by bites of certain vector ticks. The disease occurs in:
- Western and Central Europe
- the countries that made up the former Soviet Union
Human infections follow bites of infected Ixodes ricimus ticks, usually in persons who visit or work in forests, fields, or pastures. The infection may also be acquired by consuming unpasteurized dairy products from infected cows, goats, or sheep.
The risk of acquiring the disease is greatest from April through August, when the tick vector is most active.
Although vaccines are available in Europe, current data does not support travelers receiving the vaccine. Instead, it is advised that travelers protect themselves by adhering to the following recommendations:
- Avoid tick-infested areas.
- Dress appropriately to avoid being bitten.
- Use repellents containing DEET, which can be applied directly on skin.
- Use permethrin on clothing and camping gear.
- Avoid unpasteurized dairy products.
The following are the most common symptoms of encephalitis caused by arboviruses. However, each individual may experience symptoms differently. Symptoms may include:
- stiff neck
- muscle trembling
- photophobia (light hurts the eyes)
The symptoms of arbovirus encephalitis may resemble other medical conditions or problems. Always consult your physician for a diagnosis.
There is no specific treatment for encephalitis and treatment is generally supportive with maintenance of respiratory and circulatory support while the infection runs its course. Specific treatment for encephalitis will be determined by your physician based on:
- your age, overall health, and medical history
- extent of the disease
- your tolerance for specific medications, procedures, or therapies
- expectations for the course of the disease
- your opinion or preference
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