Incidents

Japanese encephalitis (JE) is an acute mosquito-borne disease caused by infection with Japanese encephalitis virus (JEV). It is associated with reproductive losses and encephalitis in pigs and horses. In rare cases, JEV infection can cause disease in people.

Japanese encephalitis virus emerged on mainland Australia in 2022 and is now considered established. Detections are expected to occur seasonally between October – April, coinciding with peak mosquito activity, but may occur year-round in the tropical north. 

2024 – 2025 season: human JE cases were reported from across Vic, Qld and NSW; detections of JEV were reported in feral pigs in NSW and in piggeries in Vic, Qld and NSW. See outbreak.gov.au for more information.

Feb – March 2022 outbreak: JEV was detected in piggeries in Vic, Qld, NSW and SA. Following the detection of multiple human JEV cases from across south-eastern mainland Australia, the outbreak was declared a Communicable Disease Incident of National Significance.

Japanese encephalitis virus is predominantly maintained by transmission cycles involving mosquitoes, waterbirds and pigs. Humans and other animals, such as horses, can become infected through the bite of infected mosquitoes.

Japanese encephalitis is a nationally notifiable disease, which means you must report it if you suspect an animal is affected. Reports can be made by calling the national Emergency Animal Disease Hotline on 1800 675 888 or through contacting your local veterinarian.

More information:

• WHA Fact Sheet on Japanese Encephalitis virus
• Department of Agriculture, Fisheries and Forestry website – Japanese encephalitis - including specific advice relating to pigs and horses.
• Animal Health Australia – Japanese Encephalitis resources, AUSVETPLAN and links to each state and territory.
• For updates on human health impacts visit Australian Government Department of Health
• For Work Health and Safety guidance on JEV visit Safe Work Australia
• National Feral Pig website
• The role of waterbirds in Australia’s 2022 Japanese Encephalitis outbreak
  • This report was prepared by BirdLife Australia on behalf of Wildlife Health Australia for the Australian Department of Agriculture, Fisheries and Forestry (DAFF).
  • Summary: The unexpected emergence and spread of Japanese encephalitis virus (JEV) in Australia in 2022 prompted DAFF and WHA to begin investigations into the wildlife origins and mechanisms of spread. Given the role of waterbirds as reservoir hosts of JEV, WHA facilitated a meeting of national and regional waterbird ecologists to identify data and information that could contribute to biosecurity and health planning and response for JEV. This report builds on the initial engagement provided by the waterbird expert workshop and further investigates the potential role of waterbirds in the 2022 outbreak.
  • Citation: Purnell, C (2022). The role of waterbirds in Australia’s 2022 Japanese Encephalitis outbreak – a rapid synthesis. BirdLife Australia, Carlton.