Japanese Encephalitis

Second Man Dies from Japanese Encephalitis in New South Wales

A second man has died from Japanese encephalitis virus in New South Wales on March 6, the state’s health authorities confirmed on Friday. The man, aged in his 70s, 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 by Queensland health authorities on Saturday.

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

What is Japanese Encephalitis Virus?

Japanese encephalitis is one of the most serious diseases spread by 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, be life-threatening.

There is 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 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.

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, providing 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