A second man has died from Japanese encephalitis virus in New South Wales on March 6, the state’s health authorities confirmed on Friday. Aged in his 70s, the man was infected while holidaying in the Murrumbidgee region.

This follows the death of another man in his 70s in Sydney last month, after holidaying in the same region in January.

Japanese encephalitis virus has also been detected for the first time in mosquitoes collected in Brisbane’s eastern suburbs, Queensland health authorities confirmed on Saturday.

With mosquito activity expected to increase thanks to flooding rains brought by Ex-Tropical Cyclone Alfred, it’s important to protect yourself from mosquito bites.

A quick refresher on Japanese encephalitis virus

Japanese encephalitis is one of the most serious diseases that spreads via mosquitoes, with around 68,000 cases annually across Southeast Asia and Western Pacific regions.

The virus is thought to be maintained in a cycle between mosquitoes and waterbirds. Mosquitoes are infected when they feed from an infected waterbird. They then pass the virus to other waterbirds. Sometimes other animals, and people, can be infected.

Pigs are also a host, and the virus has spread through commercial piggeries in Victoria, NSW and Queensland. (But it poses no food safety risk.)

Feral pigs and other animals can also play a role in transmission cycles.

What are the symptoms?

Most people infected show no symptoms.

People with mild cases may have a fever, headache and vomiting.

In more serious cases – about one in 250 people infected – people may have neck stiffness, disorientation, drowsiness and seizures. Serious illness can have life-long neurological complications and, in some cases, the infection can be life-threatening.

There’s no specific treatment for the disease.

When did Japanese encephalitis get to Australia and why is it in Brisbane?

Outbreaks of Japanese encephalitis had occurred in the Torres Strait during the 1990s. The virus was also detected in the Cape York Peninsula in 1998.

There had been no evidence of activity on the mainland since 2004 but everything changed in the summer of 2021–22. Japanese encephalitis virus was detected in commercial piggeries in southeastern Australia during that summer.

This prompted the declaration of a Communicable Disease Incident of National Significance. At the time, flooding accompanying the La Niña-dominated weather patterns and a resulting boom in mosquito numbers, and waterbird populations, was thought responsible.

The virus has spread in subsequent years and has been detected in the mosquito and arbovirus surveillance programs as well as detection in feral pigs and commercial piggeries in most states and territories. Only Tasmania has remained free of Japanese encephalitis virus.

Human cases of infection have also been reported. There were more than 50 cases of disease and seven deaths in 2022.

Cases of Japanese encephalitis have already been reported from Queensland in 2025.

Due to concern about Japanese encephalitis virus and other mosquito-borne pathogens, health authorities around Australia have expanded and enhanced their surveillance programs.

In Queensland, this includes mosquito monitoring at a number of locations, including urban areas of southeast Queensland. Mosquitoes collected in this monitoring program tested positive for Japanese encephalitis virus, promoting the current health warnings.

Why is its detection in Brisbane important?

Up to now, scientists have thought the risk of Japanese encephalitis was likely greatest following seasons of above-average rainfall or flooding. This provides ideal conditions for waterbirds and mosquitoes.

But the activity of Japanese encephalitis virus over the summer of 2024–25 has taken many scientists by surprise. Before Ex-Tropical Cyclone Alfred arrived, there had been somewhat dry conditions with less waterbird activity and low mosquito numbers in many regions of eastern Australia.

However there has still been widespread Japanese encephalitis virus activity in Victoria, NSW and Queensland.

To date, Japanese encephalitis virus activity hasn’t extended to the coastal regions of southeast Queensland. The detection of the virus in suburban Brisbane may require authorities to rethink exactly where the virus may turn up next. Authorities are ramping up their surveillance to see just how widespread the virus is in the region.

Health authorities and scientists are also trying to understand how the virus moved from western areas of the state to the coast and what drives virus transmission in different regions.

There is currently no evidence the virus is active in coastal regions of northern NSW.

What can people do to protect themselves?

Avoiding mosquito bites is the best way to reduce the risk of Japanese encephalitis virus.

Cover up with long-sleeved shirts and long pants for a physical barrier against mosquito bites.

Use topical insect repellents containing DEET, picaridin, or oil of lemon eucalyptus. Be sure to apply an even coat on all exposed areas of skin for the longest-lasting protection.

Ensure any insect screens on houses, tents and caravans are in good repair and reduce the amount of standing water in the backyard. The more water there is around your home, the more opportunities for mosquitoes there are.

A safe and effective vaccine is available against Japanese encephalitis. Each state and territory health authority (for example Queensland, NSW, Victoria) have specific recommendations about access to vaccinations.

It may take many weeks following vaccination to achieve sufficient protection, so prioritise reducing exposure to bites in the meantime.

Cameron Webb, Clinical Associate Professor and Principal Hospital Scientist, University of Sydney and Andrew van den Hurk, Medical Entomologist, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

More information on vaccine eligibility and risk

Queensland, NSW and Victoria have each published information about who is at increased risk and therefore eligible for a free vaccine. This includes people who live or work in or are planning to visit specific local government areas (listed on the respective sites) AND have additional risk factors.

Additional risk factors that qualify someone for a funded vaccine vary in each state but include regularly spending time outdoor; sleeping rough or living somewhere with limited mosquito protection such as in a tent, caravan or place without insect screens; as well as proximity to a piggery, pork abattoir or pork processing plant, among others. State governments note that there is limited supply of JE vaccines.

The Victorian government says clinician should consider the possibility of JE virus infection “in patients presenting with encephalitis or a compatible illness, and particularly in those who have spent time in rural or regional Victoria, the inland riverine regions of eastern Australia or have had extensive mosquito exposure or contact with pigs within the few weeks prior to symptom onset.”

*Information in this box has been developed by Healthed and is not part of the original article.