Information for people who recently received their Japanese encephalitis serosurvey results. 

A summary of the Japanese encephalitis virus serosurvey results is now available.

Last updated: 15 September 2022


  • NSW Health
  • NSW Health Pathology
  • National Centre for Immunisation Research and Surveillance (NCIRS)

What is this study about?

Japanese encephalitis virus (JEV) has recently been found in New South Wales for the first time.

As most people infected with the virus will show no or only minor symptoms, NSW Health would like to understand how many people have been exposed to the virus in this area. This is important so we can understand the spread of the virus in New South Wales and ensure that vaccine is made available to those at most risk of exposure.

What is Japanese encephalitis?

Japanese encephalitis is a disease caused by the Japanese Encephalitis virus (JEV), which is transmitted by mosquitoes. It is a common infection in the tropical regions of Asia and was detected for the first time in NSW in late February 2022. The virus can also infect other animals, such as birds and pigs.

We do not know how this virus became present in NSW, but it is likely the warm and wet conditions contributed to increased mosquito breeding and transmission. NSW Health is collaborating with animal and wildlife specialists to understand more about how the virus arrived in NSW.

What happens when you get JEV?

Most people with JEV have no symptoms. In 1 out of 250 people infected, it can cause a severe brain infection (encephalitis), which can lead to severe and permanent disability. In countries throughout Asia, children are reported to be particularly susceptible to this brain infection, but in places such as Australia where adults have no previous exposure to the disease, all ages are susceptible to severe infection. More information can be found at Japanese encephalitis.

Why is this important?

It is important to understand JEV infection rates because it gives us a clue on how long ago the virus was introduced into New South Wales, how many people are infected and what behaviours or activities increase the risk of infection. It also helps us understand which communities and/or community groups should be prioritised for vaccination. This is important since mosquito rates are likely to increase again in the spring and summer time, and it is possible that JEV may return.

What are we asking for?

We will take a small amount of blood (approximately 1 teaspoon) from you and/or your family member and test it for antibodies in a reference laboratory in Sydney. Antibodies are developed when you have been exposed to the virus or the vaccine.

We will also ask you to complete a survey. The survey will ask questions around exposure to animals, mosquitos, vaccination and travel to countries where JEV infection is more common.

How is testing performed?

The test is performed at the NSW reference laboratory for arbovirus infections, the Institute of Clinical Pathology and Medical Research (ICPMR) at Westmead, part of Health Pathology NSW. The laboratory will screen your sample for antibodies to any arboviruses. If this is negative, you will be informed of your negative result in writing (email or SMS).

If this screening test is positive, further tests will need to be performed to identify whether the antibodies are specific to Japanese Encephalitis or another type of arbovirus infection (Barmah Forest virus and Ross River virus are common examples in NSW). A high positive to JEV antibodies indicates prior infection, and therefore immunity to infection. These tests can take some time. You will be informed of your positive result and the interpretation of the antibody test by phone.

What will happen with the results?

The results will be pooled and published together. No individual results will be published on its own. We will provide you with a summary of the published results once it’s available. Your privacy and confidentiality will be protected under the the Health Records and Information Privacy Act, 2002.

What do I get out of participating?

Participants will informed of their results of the testing. This will help you identify if you have acquired immunity from exposure or are naïve to infection. The clinic will also provide an opportunity to discuss questions about Japanese Encephalitis virus in NSW public health professionals.

If you have any concerns about the conduct of this serosurvey, please do not hesitate to contact the Health Protection Zoonoses team at

Current as at: Thursday 15 September 2022
Contact page owner: Health Protection NSW