A vaccine rollout has been launched for the mosquito-borne Japanese encephalitis in Australia.

Australia's acting chief medical officer Sonya Bennett has declared the disease an “incident of national significance”, after Queensland confirmed its first human case of the disease in more than two decades, NSW recorded what is likely to be its first human case, and at least four human cases were identified in Victoria.  

Japanese encephalitis virus (JEV) affects pigs, horses and humans. It has been confirmed at 14 piggeries across NSW, South Australia, Queensland and Victoria.

People tend to suffer either mild or no symptoms, though the virus can cause neurological complications and even death in severe cases.

Dr Bennett said less than 1 per cent of people infected with JEV develop a serious illness.

“A national working group of communicable disease, vaccine and arbovirus experts has been established to support the response, including mosquito surveillance and control measures and identification of those at direct risk, and for the rollout of vaccines,” Dr Bennett says.

“Public health communications regarding mosquito protection will target affected communities.”

The virus is spread by mosquitoes, so preventative measures include avoiding mosquito bites by using repellents containing diethyl toluamide (DEET),wearing closed-in shoes and loose, light-coloured clothing to cover arms and legs.

Local government leaders are being briefed about spraying for mosquitoes in coming weeks.

The JEV vaccine rollout is currently targeted at those deemed most at risk, including piggery workers, and experts say a widespread vaccination campaign, such as the COVID-19 vaccine rollout, is not likely to be necessary.

The virus is not transmitted between humans, and cannot be caught by eating pork or pig products.