Japanese encephalitis virus (JEV) information for health professionals

Transmission

The normal lifecycle of JE virus is between waterbirds and mosquitoes, which may then transfer over to pigs, horses and other mammals. Animals and people become infected through the bite of infected mosquitoes.

Mosquitoes involved in the transmission of JE virus are primarily Culex species. The specific species of mosquito implicated in Australia is not yet confirmed.

There is no evidence of transmission from person to person. It cannot be contracted through eating meat products.

Symptoms

Over 90% of JEV infections are asymptomatic.

Acute encephalitis is a serious manifestation and occurs in less than 1% of cases of JEV infection. This is characterised by:

  • headache
  • fever
  • seizures (usually generalised tonic-clonic)
  • focal neurological signs, and
  • depressed level of consciousness.

Acute encephalitis has a high case-fatality rate of around 30%. There is no specific treatment. Approximately half of those who survive the acute illness will have neurological sequelae.

JEV infection may also manifest as a milder undifferentiated febrile illness. It sometimes also presents as acute flaccid paralysis or aseptic meningitis.

Information for patients about signs and symptoms can be found on the Japanese encephalitis - including symptoms, treatment and prevention page.

Testing

Test for flaviviruses including JEV in persons with suspected encephalitis/meningoencephalitis without identified cause. Send the following: 

  • Serum (2 mL in children, 5-8 mL in adults) including both acute and convalescent specimens (3-4 weeks post onset) for serology for flaviviruses including JEV
  • Blood for PCR and culture for flaviviruses including JEV
  • CSF (at least 1 mL) for PCR, culture, and serology for flaviviruses including JEV
  • Urine for PCR and culture for flaviviruses including JEV.

Routine testing for serology is not recommended prior to vaccination.

Notification

Japanese encephalitis is an urgent notifiable condition that must be notified immediately to SA Health if suspected or confirmed by medical practitioners and pathology services by phoning the Communicable Disease Control Branch on 1300 232 272.

Treatment for Japanese encephalitis virus

There is no specific treatment for infection with Japanese encephalitis virus. Serious illness with encephalitis requires management in hospital.

Prevention of Japanese encephalitis virus

  • Vaccination against JEV is available but not funded. Immunisation against JEV will not protect people from other mosquito borne diseases. For more information about the JEV vaccine speak with your healthcare provider or see the Australian Immunisation Handbook — Japanese encephalitis chapter.
  • People should take steps to limit their exposure to mosquitoes. There are simple steps people can take to protect themselves against mosquito-borne diseases. For more information, see Mozzies suck.
  • Exclusion from childcare, preschool, school or work is not necessary.
  • All people who work with potentially infected animals or work in areas in which infected mosquitos may be present should wear appropriate personal protective equipment (PPE). The PPE should be chosen based on the assessed level of risk and the task.