Japanese encephalitis

Japanese encephalitis is caused by the Japanese encephalitis virus, which is spread by the bite of an infected mosquito. The risk of Japanese encephalitis in Aotearoa New Zealand is low.

April 2022: There have been recent reports of Japanese encephalitis in Australia 

The risk of Japanese encephalitis in Aotearoa New Zealand is low. 

If you experience any of the symptoms described below after visiting Australia’s southeast, seek urgent medical care.

What is Japanese encephalitis?

Japanese encephalitis is caused by the Japanese encephalitis virus (JEV). The virus is spread by the bite of an infected mosquito and is more common in areas of increased mosquito activity such as parts of Asia and the Torres Strait region of Australia. 

Image: Canva

Most people infected with the JEV will not have symptoms, but on rare occasions it can result in severe disease and even death. It cannot be transmitted from human to human, or by eating meat from an infected animal.

What are the symptoms of Japanese encephalitis?

Most people infected with the JEV do not have symptoms, or have mild symptoms. Less than 1% of people infected with JEV develop symptoms of inflammation of the brain (encephalitis).

  • In persons who develop symptoms, the incubation period (the time from infection until illness) is typically 5–15 days.
  • The first symptoms often include fever, headache and vomiting.
  • Mental status changes, disorientation, tremor, weakness, and movement disorders might develop over the next few days.

If you believe you may be infected with the Japanese encephalitis virus, seek urgent medical assistance. 

How is Japanese encephalitis diagnosed?

Japanese encephalitis is confirmed through a combination of laboratory testing and clinical examination. If you think you may be infected with the Japanese encephalitis virus seek medical help urgently. 

How is Japanese encephalitis treated?

There are no treatments for Japanese encephalitis. You can relieve the symptoms by getting plenty of rest, drinking plenty of liquids and taking paracetamol for pain or fever.

In more severe cases, hospitalisation for supportive care and close observation may be needed.

How to prevent Japanese encephalitis?

There are 2 ways to prevent Japanese encephalitis:

  • receiving a vaccination for the virus. Check with your local travel clinic if you need this vaccine before you travel.   
  • avoiding being bitten by mosquitos. Read more about insect repellents.

Learn more

Countries in which Japanese encephalitis virus has been identified CDC, US
Japanese encephalitis CDC, US

References

  1. Japanese encephalitis Australian Government Department of Health
Credits: Health Navigator Editorial Team.