What is Japanese Encephalitis Virus?

Japanese encephalitis virus is a virus in the Flaviviridae family found distributed through Japan and many other regions of eastern and southern Asia, like Korea. This virus is a leading cause of infectious encephalitis in this region, particularly among children, and travelers to the region can be at risk of contracting it if they have not been previously exposed. A vaccine is available to prevent Japanese encephalitis infection, and patients with concerns about this virus can discuss the vaccination with their doctors.

This virus contains a single strand of RNA. It lives naturally in reservoirs of wading birds and pigs, where the virus amplifies and becomes more virulent. Mosquitoes feed on these animals and pick up the virus along the way, transmitting it to people when they feed on humans. People do not contract the virus from close personal contact with infected individuals, only from mosquito bites. Programs to control the Japanese encephalitis virus usually involve suppressing mosquito populations and limiting contact between humans and insects. This can also prevent the transmission of other infectious diseases, like malaria.

The virus can incubate for up to two weeks. Many people have only a mild case of Japanese encephalitis, experiencing a headache and fever for a few days. Supportive care can include providing the patient with fluids and rest, as well as offering pain management if the headache becomes intense. In severe cases, patients will experience tremors, seizures, coma, and other neurological problems. The mortality rate for people with severe infections can be as high as 60%.

Many people in the native range of the Japanese encephalitis virus contract the disease during childhood and acquire an immunity. Others may receive vaccinations before they get sick. These should protect the patient for life from Japanese encephalitis virus infections. In the event of a severe infection, the patient may need treatment in a hospital, where care providers can carefully monitor him and provide appropriate interventions as neurological problems develop.

The Japanese encephalitis virus is closely related to the West Nile virus. Cases outside its native range are very rare, and usually the result of someone traveling to Asia and unwittingly carrying the virus home. When people who have recently been traveling get sick, it is important to let the doctor know about the travel, as the doctor may rule out a diagnosis like Japanese encephalitis if she thinks the patient has not been to Asia recently.