JEV is transmitted by mosquitoes that occur across much of Asia. Whilst rare, infection with JEV can result in a disease known as Japanese encephalitis (JE), both in humans and animals, including pigs and horses.
The transmission cycle of JEV involves mosquito vectors and vertebrate hosts. Water birds (particularly water wading birds e.g., herons, egrets and bitterns) and pigs are the most important amplifying hosts. Humans and other animals, such as horses, are generally considered incidental hosts, as they do not contribute to ongoing transmission of the virus.
JEV had not previously been detected in Australia outside of the Torres Strait, far north Queensland and Tiwi Islands in the Northern Territory.
In March 2022, JEV was detected in the southeast of Australia for the first time. Affected jurisdictions, including New South Wales, Victoria, Queensland and South Australia reported JEV in several piggeries. Mosquito and feral pig detections have since been reported across several States and Territories, including the Northern Territory.
More than 45 confirmed or probable human cases of JE have now been reported in these jurisdictions since December 2022 (no cases have been reported from WA), although there have been no human cases reported in 2023.
The WA Department of Health confirmed detection of antibodies to JEV in sentinel chicken flocks in the Kimberley and Pilbara regions, as well as feral pigs in the northern Kimberley, during 2023. These results indicate the virus has been active within WA and presents a potential risk to public health, particularly in the Kimberley region.
The Department of Health is working with PathWest and the Department of Primary Industries and Regional Development (DPIRD), as well as interstate and national colleagues and committees, as part of a coordinated national response.
For updated information on the national JEV response, please visit the outbreak website (external site).