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Japanese Encephalitis

Japanese encephalitis (JE) is a viral disease of the central nervous system caused by the Japanese encephalitis virus and is transmitted through the bite of mosquitoes. Most people develop no symptoms with the illness and it resolves by itself. When symptoms do develop it can range from fever and mild headache to disorientation, seizures and paralysis.

Where does it occur?

This disease is seen from the Indian subcontinent eastward involving all of South East Asia, China, Korea, Japan, Pacific islands and Northern Queensland in Australia. Map

How is it transmitted?

The illness is spread by the bite of the Culex family of mosquitoes. These mosquitoes are quite prevalent in rural areas, especially in stagnant waters of paddy fields etc and increase in numbers during the rainy season.

Is it contagious from person to person?

It is not contagious from person to person.

What is the risk for travelers?

The highest risk is for those planning prolonged travel (>4 weeks) to rural and agricultural areas and is estimated to be 1: 5000 per month of exposure. For all other travelers the risk is generally low.

How soon after exposure will one develop symptoms?

Symptoms develop 1-2 weeks after exposure.

What are the signs and symptoms?

In mild cases the symptoms are fever, muscle pain and headache that resolve after a few days.

Approximately 1: 300 infections result in a serious illness called encephalitis. Symptoms progress to nausea, vomiting, restlessness, drowsiness, coma, seizures and paralysis. There is a 20-50% chance of death with encephalitis and nearly 70% of survivors have persistent neurological deficits.

Are there any lab tests to diagnose the illness?

Blood and spinal fluid antibody tests are available to make a definitive diagnosis.

Is there any treatment?

Treatment is entirely supportive; there is no specific anti-viral medication against Japanese encephalitis virus at this time.

What preventive measures can be taken?

Japanese encephalitis vaccine is available and is advisable for long-term travelers (>4 weeks) or for short-term travelers who will be in rural and agricultural areas of high-risk countries.

Approximately 0.6% of vaccine recipients can develop an anaphylactic reaction (rash, swollen lips and throat, difficulty breathing) within minutes to nearly a week after the vaccine is given.

One should also strictly follow mosquito precautions:

Avoid outdoor activity in the evening and night

Stay in accommodations with screens on windows and doors

Wear long sleeve shirts, pants and socks

Apply insect repellant containing DEET to exposed skin and clothing

Use permethrin impregnated fine mesh mosquito nets

Use mosquito repellant coils or insecticide in your room.

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