Japanese encephalitis - including symptoms, treatment and prevention

This is a viral infection of the human brain caused by the Japanese encephalitis (JE) virus.

The risk of Japanese encephalitis to travellers depends on the season of travel, the areas visited, the duration of travel, outdoor activities planned and measures used to avoid mosquito bites.

Japanese encephalitis is a notifiable condition1

How Japanese encephalitis virus is spread

The Japanese encephalitis virus is spread by particular types of mosquitoes. Although most cases in Australia are diagnosed in people returning from overseas travel, there have been some locally acquired cases diagnosed in the Torres Strait and in Cape York, Queensland.

Pigs are an important host for the virus, where it can multiply to very high levels in their blood. Mosquitoes that feed on infected pigs can become infected with the virus and then transmit it to humans.

Signs and symptoms

Symptoms in humans include:

  • headache
  • fever
  • seizures (fits)
  • coma.

While most people with Japanese encephalitis have no symptoms, the disease can be serious, causing encephalitis (infection or inflammation of the brain), permanent damage to the nervous system or death.

Diagnosis of Japanese encephalitis virus

Diagnosis is usually made by a blood test. Other illnesses with similar symptoms may need to be excluded by other tests.

Incubation period

(time between becoming infected and developing symptoms)

Usually 5 to 15 days.

Infectious period

(time during which an infected person can infect others)

There is no evidence of person to person spread.

Treatment for Japanese encephalitis virus

There is no specific treatment for Japanese encephalitis. Treatment involves management of the symptoms.

Prevention of Japanese encephalitis virus

  • Exclusion from childcare, preschool, school or work is not necessary but people who are infected should avoid being bitten by mosquitoes while they are unwell.
  • Personal protection and the environmental management of mosquitoes are important in preventing illness. For information on how to protect yourself, see Fight the Bite.


A vaccine is available that provides protection against Japanese encephalitis. Three injections are required over a 1 month period which gives protection for about 3 years. A travel medicine doctor will be able to give advice on immunisation.

Useful links

1 – In South Australia the law requires doctors and laboratories to report some infections or diseases to SA Health. These infections or diseases are commonly referred to as 'notifiable conditions'.