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Encephalitis is an inflammation of the brain that is frequently caused by a viral infection. The arboviruses cause encephalitis and are transmitted to people and animals by insects.
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 tick-borne encephalitis.
Japanese encephalitis is a mosquito-borne viral disease that occurs mainly in:
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.
Tick-borne encephalitis is a viral infection of the central nervous system transmitted by bites of certain vector ticks. The disease occurs in:
Human infections follow bites of infected Ixodes ricinus 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.
The arboviruses that cause encephalitis are transmitted to people and animals by insects. In rural areas, arboviruses that are carried by mosquitoes or ticks are the most common cause of arboviral infection, which is often mild, but can progress to encephalitis.
The following are the most common symptoms of encephalitis caused by arboviruses. However, each person may experience symptoms differently. Symptoms may include:
The symptoms of arbovirus encephalitis may resemble other medical conditions or problems. Always consult your doctor for a diagnosis.
The majority of human infections are asymptomatic or may result in a flu-like syndrome. Onset may be gradual or sudden with symptoms including: fever, headache, myalgias, malaise, and occasionally extreme physical weakness. Infection may, however, lead to encephalitis or inflammation of the brain. Encephalitis may result in death or have permanent neurological repercussions. Fortunately, only a small proportion of infected people progress to frank encephalitis.
Blood tests and cerebrospinal fluid analysis are used to isolate and identify the virus.
Experimental research has shown that invasion of the central nervous system (CNS), generally follows initial virus infection. Because the arboviral encephalitides are viral diseases, antibiotics are not effective for treatment and there are no effective antiviral drugs at this time. There is no specific treatment for encephalitis and treatment is relieving symptoms and maintaining respiratory and circulatory support while the infection runs its course. Specific treatment for encephalitis will be determined by your doctor based on:
A vaccine for Japanese encephalitis is currently available in the United States through most travelers' clinics. The Centers for Disease Control and Prevention 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:
In addition, travelers to rural areas should bring a portable bednet and apply permethrin, a mosquito repellent/insecticide to both the bednet and clothing.
Another way to prevent encephalitis is with mosquito control. In many emergency situations, the method to achieve maximum results over a wide area is with aerial spraying. In many states, aerial spraying may be available in certain locations as a means to control nuisance mosquitoes. Such resources can be redirected to areas with virus activity.
For tick-borne encephalitis, it is advised that travelers protect themselves by adhering to the following recommendations:
Arbovirus encephalitis is generally managed according to the severity of the presenting symptoms. Supportive care is used since there is no definitive treatment for encephalitis.
Notify your provider if you have the following symptoms:
Arbovirus treatment is generally supportive with maintenance of respiratory and circulatory support while the infection runs its course.
Tips to help you get the most from a visit to your health care provider:
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