Four states are taking part in a national study to determine how many people have been exposed to the Japanese encephalitis virus to better inform control efforts.

The National Centre for Immunisation Research and Surveillance is leading the surveillance program with surveys being undertaken in South Australia, regional Victoria, NSW and central Queensland.

The survey involves looking at blood samples to measure immunity due to past infection or vaccination.

South Australian Chief Public Health Officer Nicola Spurrier said as most people infected with the Japanese encephalitis virus would show no or only minor symptoms the study would help health officials better understand how many people had actually been exposed.

"It will allow us to better understand the spread of the virus, as well as the different risk factors, so we can ensure that the vaccine is made available to those at most risk of exposure," Professor Spurrier said.

"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."

Japanese encephalitis virus is a rare but serious disease transmitted by mosquitoes and 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, such as along the River Murray.

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

Anyone interested in taking part in the study will be asked to donate a small amount of blood and complete a short questionnaire about any exposure to animals, mosquitoes and the vaccine and any travel to countries where the infection is more common.

The blood sample will be screened in Sydney, to determine if the person had been infected with the virus previously.

Prof Spurrier said while vaccination was available to those most at-risk, everyone was 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," she said.

On the latest federal government figures available there have been 32 confirmed cases of Japanese encephalitis virus in Australia since the beginning of January last year - 13 in NSW, 10 in Victoria, five in SA, two in Queensland and two in the Northern Territory.

There have been a further 10 suspected cases - four in SA, three in Queensland and three in Victoria.