What Areas in Australia Are Most at Risk for Japanese Encephalitis?

Over the past few summers, Australia has seen a noticeable increase in mosquito activity — and with it, a rise in mosquito-borne diseases. One virus in particular has drawn national attention: Japanese Encephalitis (JE). Traditionally considered a rare infection in Australia, JE has now been detected earlier and in more regions than health authorities expect, prompting warnings across New South Wales, Victoria, and parts of northern Australia.

Japanese Encephalitis is carried by mosquitoes that have previously fed on infected animals, such as waterbirds or pigs. It cannot spread from person to person, but when conditions are right — warm weather, persistent humidity, standing water, and active mosquito populations — the virus can circulate more easily in the environment. In severe cases, JE can cause inflammation of the brain (encephalitis), making awareness and prevention especially important.

This season, early detections in mosquito traps and sentinel animal programs have highlighted that some areas of Australia face a much higher risk than others, as reported by the Daily Mail.

What is Japanese Encephalitis and how is it spread?

Japanese Encephalitis (JE) is a mosquito-borne viral infection that affects both animals and humans. While most people infected never develop symptoms, a small percentage can experience serious illness, including inflammation of the brain (encephalitis), which makes prevention and awareness extremely important.

How the virus circulates in nature

JE is maintained in a natural cycle between:

• Mosquitoes (primarily Culex species),
  
• Waterbirds (such as herons and egrets), and
  
• Pigs, which act as “amplifying hosts” because the virus replicates efficiently in them.

Mosquitoes pick up the virus when they bite infected animals. Humans become infected the same way — through the bite of an infected mosquito.

Importantly:

• JE does not spread from person to person.
  
• People cannot get JE from eating pork or from direct contact with infected animals.

Why JE is appearing more often in Australia

A combination of environmental and seasonal factors has made JE more visible across Australia in recent years:

• Warmer springs and earlier summers produce ideal breeding conditions for mosquitoes.
  
• Flooding and increased rainfall create large areas of standing water where mosquitoes thrive.
  
• Pig farms and wetlands in certain regions support the virus’s natural transmission cycle.
  
• Higher mosquito populations increase the chance of human exposure — even if infection numbers remain low.

Health authorities have noted that early detections this season are particularly concerning, as JE was identified in mosquito traps and sentinel animal samples sooner than expected.

Symptoms to be aware of

Most infected people will never know they had JE. But those who do develop symptoms may experience:

• Fever
  
• Headache
  
• Fatigue
  
• Vomiting
  
• Confusion or neurological symptoms in severe cases

Severe illness is rare but can be life-threatening, which is why understanding risk locations and prevention strategies is essential.

The areas of Australia most at risk for Japanese Encephalitis (Overview)

While Japanese Encephalitis can technically occur anywhere mosquitoes are present, the highest-risk locations in Australia share a few important features:

• Warm, humid climates
  
• Large mosquito populations
  
• Wetlands, rivers or floodplains
  
• Proximity to piggeries or waterbird habitats

Recent surveillance by NSW and Victorian health authorities — including findings reported in the media — shows that JE detections are appearing earlier in the season and across a wider range of regions than previously recorded.

The 2025–2026 season saw JE detected in mosquito surveillance traps earlier than expected, including:

• Mosquitoes collected in Horsham, Victoria,
  
• A sentinel chicken blood sample collected in Cowra, NSW.

Early-season detections like these suggest:

• Mosquitoes carrying the virus are active sooner than normal
  
• Weather conditions are supporting faster mosquito population growth
  
• More regions may face elevated JE risk this summer

High-risk areas in NSW

New South Wales currently has one of the largest concentrations of LGAs classified as high risk for Japanese Encephalitis. Health authorities have confirmed around 60 LGAs where environmental conditions, mosquito activity, and historical detections increase the likelihood of JE transmission.

These areas are mostly located west of the Great Dividing Range, but several regions in northern and inland NSW are also affected.

 

These LGAs are considered higher risk because sentinel surveillance — such as mosquito trapping and blood testing in sentinel chickens — has repeatedly detected JE or related flaviviruses like Kunjin virus in these areas.

Vaccination availability

NSW Health provides free JE vaccinations for eligible residents in high-risk LGAs, especially those living or working outdoors or near waterways.Many residents may need to book ahead or speak to a GP or pharmacist, as demand can increase during summer.

Victoria — Early detections and expanding risk zones

Victoria has also recorded early signs of Japanese Encephalitis circulation, with the first detection of the season confirmed in Horsham, located in the state’s west. Health authorities say this early-season activity is a warning sign, as it indicates that mosquito populations are becoming active sooner than usual, increasing the potential for transmission throughout summer.

Key regions in Victoria with elevated JE risk

Based on past outbreaks, recent surveillance, and environmental conditions, the following areas are considered higher risk:

• Horsham (where early-season JE was detected)
  
• Swan Hill
  
• Mildura
  
• Gannawarra
  
• Loddon
  
• Campaspe
  
• Moira
  
• Wodonga
  
• Shepparton region
  
• Murray River border communities

Many of these regions have previously reported activity from other flaviviruses such as Murray Valley encephalitis (MVEV) and Kunjin virus, both of which share ecological similarities with JE.

Vaccination in Victoria

Victoria offers JE vaccinations for higher-risk groups, which typically include:

• People working with pigs or in piggeries
  
• Outdoor workers in affected LGAs
  
• Residents living near areas with confirmed mosquito detections

People are advised to contact their GP, pharmacist, or local council health services for eligibility and availability.

For more information on vaccination eligibility and availability, check out Victoria Department of Health website here.

Queensland — Long-term endemic risk zones

Queensland has long been recognised as a region with naturally high mosquito activity, making it more vulnerable to mosquito-borne viruses, including Japanese Encephalitis. While JE detections in Queensland have been less frequent compared to NSW and Victoria, the environmental conditions in many parts of the state create an ongoing baseline risk.

Why Queensland is considered an endemic risk area

Several environmental and ecological factors contribute to Queensland’s elevated risk:

• Tropical and subtropical climate, which supports mosquito breeding for most of the year
  
• Frequent rainfall and wet seasons, leading to widespread standing water
  
• Extensive wetlands, rivers, and floodplains, particularly in the north
  
• Waterbird migration routes, which help spread flaviviruses
  
• Agricultural settings, including regions with piggeries

Regions in Queensland with higher risk

While JE cases have been uncommon in Queensland, certain areas are considered more at risk due to climate, geography, and historical virus activity:

• Far North Queensland (Cairns, Cape York, Gulf Country)
  
• Northern and central coastal regions
  
• Gulf of Carpentaria communities
  
• Western QLD during wet or flooding periods
  
• Agricultural regions with piggeries or wetlands

Vaccination availability

Queensland Health may offer free JE vaccination to people living or working in high-risk northern areas. Residents are encouraged to speak to their GP or pharmacist to check eligibility.

Check information on vaccination by visiting the Queensland Health website here.

South Australia

South Australia is not typically the first state people think of when it comes to mosquito-borne diseases, but the Riverland region and surrounding wetland areas create conditions that allow flaviviruses — including Japanese Encephalitis — to circulate when mosquito numbers rise.

While SA has recorded fewer JE detections than eastern states, health authorities still classify several regions as higher risk, particularly following seasons of flooding or heavy rainfall.

SA regions with elevated JE risk

Based on environmental risk factors and previous flavivirus activity, the following areas are monitored closely:

• Riverland region (Renmark, Berri, Loxton, Waikerie)
  
• Lower Murray wetlands
  
• Eyre Peninsula wetlands
  
• Limestone Coast waterways

These locations experience seasonal increases in mosquito numbers, particularly after periods of heavy rain or flooding.

Vaccination availability

South Australia provides JE vaccination for eligible higher-risk groups. Residents can check eligibility through SA Health or consult their GP.

Northern Territory

The Northern Territory (NT) has some of the most favourable conditions in Australia for mosquito breeding, making it a region where mosquito-borne viruses — including Japanese Encephalitis — can circulate more easily. While JE detections in the NT may vary from year to year, the environmental and climatic conditions create an ongoing baseline risk that health authorities monitor closely.

Regions in the NT with higher JE risk

Although risk can fluctuate with climate and rainfall, the following regions typically face higher concern:

• Darwin and surrounding rural areas
  
• Katherine region
  
• Arnhem Land
  
• Gulf of Carpentaria side communities
  
• Top End wetlands, including Kakadu and Mary River
  
• Communities close to coastal floodplains or freshwater wetlands

These areas often record heavy mosquito activity and periodic detections of other flaviviruses, such as Murray Valley encephalitis (MVEV).

Seasonal risk patterns in the NT

JE risk climbs during:

• The wet season (November–April)
• Periods of prolonged standing water
  
• Cyclone or monsoon events, which dramatically increase mosquito breeding
  
• Seasons with large feral pig populations near wetlands or floodplains

Because JE can circulate silently in wildlife, the NT relies heavily on ongoing mosquito surveillance.

Vaccination availability

The NT government may offer free JE vaccinations for certain high-risk groups.Anyone unsure about their eligibility should speak with their local health clinic, pharmacist, or GP.

Western Australia

Western Australia (WA) experiences a distinct wet–dry seasonal pattern, especially in the north. This climate creates the perfect conditions for mosquitoes to thrive, making Kimberley and Pilbara key regions to watch for Japanese Encephalitis risk.

Although JE activity in WA has been less frequent than in eastern states, the state’s environmental and climatic profile means that risk can increase rapidly whenever the right conditions align.

Areas in WA with elevated risk

Based on environmental factors, climate, and past mosquito surveillance, the following regions are monitored closely:

• Kimberley region (Broome, Derby, Kununurra, Wyndham)
  
• Pilbara region (Port Hedland, Karratha, Newman, coastal stretches)
  
• Gascoyne floodplains after heavy rainfall
  
• Remote inland wetlands and river corridors

Mosquito-borne diseases — including Murray Valley encephalitis — are already known to occur in these areas, reinforcing the need for vigilance.

Vaccination availability

WA may offer free JE vaccination to:

• Outdoor workers
  
• People in remote communities
  
• Workers in piggeries or livestock settings
  
• Residents in targeted northern regions during heightened-risk periods

Eligible individuals should consult WA Health, their pharmacist, or their GP.

For more information, visit the Government of Western Australia Department of Health’s website here.

Conclusion — Staying protected as JE risk rises across Australia

Japanese Encephalitis is still considered a rare disease in Australia, but recent early detections across NSW, Victoria, and the northern regions highlight a clear message: the environmental conditions that allow JE to spread are becoming more favourable each summer. Places with warm weather, wetlands, floodplains, waterbirds, and agricultural activity — especially piggeries — are the areas at highest risk.

The good news is that JE is preventable. Understanding which regions are most affected helps you make informed decisions, whether you’re travelling, working outdoors, camping, or living in a known mosquito-heavy area. Simple protective measures such as using repellent, wearing long clothing, improving home mosquito barriers, and staying updated with state health alerts make a significant difference.

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