Japanese encephalitis is a rare but serious disease caused by the Japanese encephalitis virus.
It is spread to humans by infected mosquitoes.
Japanese encephalitis virus (JEV) can be acquired in South Australia but is rare.
For updated case numbers see Surveillance of Notifiable Conditions.
Japanese encephalitis is a notifiable condition1
The Japanese encephalitis virus is transmitted to humans through bites from Culex mosquitoes, which have been infected with Japanese encephalitis virus. Culex mosquitoes are commonly found in South Australia. The virus exists in a transmission cycle between mosquitoes, pigs and/or water birds.
Pigs are an important host for the virus. The virus can occur at high levels in their blood for 4-6 days. Mosquitoes that feed on infected pigs during this period can become infected with the virus and then transmit it to humans.
It cannot be transmitted by eating meat of infected animals. It cannot be spread from person to person.
Most people with Japanese encephalitis virus infection do not experience any illness. There may be mild symptoms such as fever and headache.
A small proportion will have encephalitis (inflammation of the brain). This may begin with symptoms such as:
Confusion, unusual behaviour, sleepiness, seizures, weakness, and abnormal movements may develop. Encephalitis can cause permanent damage to the nervous system or death.
Diagnosis is usually made by a blood test or sample from the spinal fluid. If you have been infected, you do not put others at risk.
If you have symptoms consistent with Japanese encephalitis, seek medical attention.
If you have any severe signs such as headache, vomiting, confusion, paralysis or seizures you should call 000 immediately.
An incubation period is the time between becoming infected and developing symptoms.
Symptoms, if they occur, usually develop 5 to 15 days after being bitten by infected mosquitoes.
There is no specific treatment for infection with Japanese encephalitis virus. Serious illness with encephalitis requires management in hospital.
Japanese encephalitis virus vaccination is funded for certain groups.
For more information visit the Japanese encephalitis virus (JEV) vaccine page.
Vaccination for the Japanese encephalitis virus is also recommended for travellers spending one month or more in rural areas of countries with a high-risk for Japanese encephalitis.
Immunisation against JEV will not protect people from other mosquito borne diseases.
There are simple steps all people should take to protect themselves against mosquito bites and mosquito-borne diseases, including:
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'.
