SA joins national Japanese Encephalitis study

02 December 2022

South Australians are being invited to take part in a national study to help determine how many people have been exposed to the Japanese encephalitis virus (JEV) to inform control efforts.

The National Centre for Immunisation Research and Surveillance (NCIRS) is leading a national human JEV Serosurveillance Program, with serosurveys also taking place in regional Victoria, New South Wales and Central Queensland.

A serosurvey is a survey of blood samples collected from the population, to measure immunity due to past infection or vaccination.

Japanese encephalitis is a rare but serious disease caused by the Japanese encephalitis virus which is transmitted by mosquitoes and was first detected in SA in early 2022. The virus can also infect other animals, such as birds and pigs.

As part of a national response to this outbreak, a targeted vaccination campaign has been rolled out to eligible people who live and work in high-risk areas along the River Murray and Lower Lakes.

A small number of people infected with JEV (around 1 in 250) will develop encephalitis or inflammation of the brain, which can cause permanent damage to the nervous system or death.

However, most people infected with JEV experience only mild symptoms or no illness at all.

Therefore, while nine cases of JEV have so far been detected in SA, this study will help to determine the true extent of JEV in the community.

The serosurvey is being delivered by the Riverland Academy of Clinical Excellence (RACE) Public Health Unit in partnership with SA Pathology, with operations to be deployed at selected SA Pathology collection sites in Murray Bridge, Mannum, Tailem Bend, Berri, Loxton, Barmera, Waikerie, and Renmark.

Anyone interested in taking part in the study will be asked to donate a small amount of blood and complete a short questionnaire which will ask questions around exposure to animals, mosquitoes, JEV vaccination and travel to countries where JEV infection is more common.

The blood sample will then be screened by the NCIRS in Sydney, to see whether the person has been infected with the virus before or not.

It follows a separate serosurvey undertaken in September which involved testing blood donations for JEV that were taken by LifeBlood at mobile sites in the Riverland and metropolitan Adelaide.

This latest SA study is expected to run until 30 June 2023, with the results to inform targeted public health interventions.

For more information on the JEV vaccine rollout, go to

Quotes attributable to Chief Public Health Officer, Prof Nicola Spurrier:

As most people infected with the Japanese encephalitis virus will show no or only minor symptoms, this study will help us to understand how many people have actually been exposed to the virus in high-risk areas of our state.

It will allow us to better understand the spread of the virus in South Australia, as well as the different risk-factors, so we can ensure that the vaccine is made available to those at most risk of exposure.

This is particularly important as we enter what is expected to be another wet summer, which means more mosquitoes around, and therefore a higher risk of mosquito-borne disease.

While vaccination is available to those most at-risk, everyone is encouraged to take precautionary measures to avoid mosquito bites, including using mosquito repellent and wearing loose and long sleeve clothing. You should also avoid storing stagnant water around your home as mosquitoes can easily breed in a small amount of water and use insect screens if doors and windows are kept open.