Japanese Encephalitis Warnings in NSW & Victoria

Travellers to the Riverina areas of NSW should take note of a health warning regarding japanese encephalitis.  The warning was issued mid-January 2026 and relates to a probable case who had travelled to an area of risk in late December.  

NSW Health also noted the presence of the virus in a sentinel chicken sample taken early January in the Upper Lachlan Shire near Goulburn. A similar message was issued by the Department of Health in Victoria when the virus was detected in sentinel chickens in the Horsham area in December 2025. 

Japanese encephalitis is a notifiable disease in Australia. Eight cases were notified in 2025 – the majority in the first few months of the year.

The above case would be the first notification of 2026.  

What is Japanese Encephalitis?

Japanese encephalitis is a viral disease transmitted by mosquitos from birds and pigs to humans. It is the leading cause of vaccine preventable encephalitis in Asia.  

This mosquito vector breeds in areas of ground water. In temperate climate areas such as China and Nepal, cases occur mostly during the monsoon months. Most infected bites do not cause disease but about 1 in 250 infections will result in symptomatic disease with a high rate of death or permanent disability (50%).  

Japanese Encephalitis in Australia - an emerging public health risk

Japanese encephalitis was identified for the first time in the Murray lands of southern Australia in 2022.

The northern and southern river systems became connected after 3 consecutive La Nina seasons. This allowed wetland birds (herons, egrets etc) to bring the disease south. Previously it was only considered an Australian risk in the Torres Strait and Cape York

A serological survey of Japanese encephalitis past exposure was undertaken in regional NSW (Balranald, Corowa, Dubbo, Grifith and Temora) during June-July 2022.  The results are interesting. Evidence of past infection was found in 8.7% of participants whose ages ranged from 20 to 87 Years. 

Vaccination and prevention of Japanese Encephalitis

Primary prevention always rests with mosquito avoidance measures. However, two excellent vaccines are available in Australia (Imojev, Jespect). 

Japanese Encephalitis vaccination is available at no cost for individuals considered to be at a higher risk of the disease. This eligibility is mostly based on residential or occupational risk.

For more information, see:

• NSW Health - Japanese encephalitis virus (JEV) vaccination
• Victoria - Japanese encephalitis
• SA Health - Japanese encephalitis virus (JEV) vaccination

Japanese encephalitis (JEV) risk for international travellers

There are currently 24 countries in the South-East Asia and Western Pacific regions that have Japanese Encephalitis transmission risk. More than 3 billion people live in endemic areas. The World Health Organization (WHO) states that major outbreaks of Japanese Encephalitis occur every 2-15 years.

The incidence of JEV cases in Japan, Republic of Korea and some regions in China, Nepal, Sri Lanka, Thailand and Vietnam have declined in recent years, largely because of immunisation.

For most travellers to Asia and parts of the Western Pacific, the risk of Japanese Encephalitis is low, particularly for short term visitors to urban areas.

This risk is estimated to be less than 1 in a million per month of stay but will change according to season, destination, duration of travel and intended activities.

Environmental risk factors for transmission

Environmental determinants of Japanese Encephalitis prevalence include climate, rainfall, temperature, wind, water bodies, and the proximity to irrigation and pig farming.

Japanese Encephalitis is most prevalent in rural or agricultural areas, often associated with rice farming, as the breeding grounds for the transmitting mosquito rely on adequate supply of water.

• In temperate regions of Asia, transmission is seasonal, with peak cases of infection in the summer and autumn months. 
• In the tropics and subtropics, transmission can occur year-round, peaking during the wet season. 

Mosquito biting habits and prevention advice

Travellers should be reminded of the risk of mosquito borne disease and individual mosquito biting habits. Mosquitoes transmitting Japanese encephalitis are most active at dusk and dawn and accommodation plays an important role in prevention with nighttime biters.