Flooding raises encephalitis virus warnings in eastern Australia

A rise in suspected cases of Japanese encephalitis virus in eastern states hit by rain and floods has triggered a national health response.

Health experts have urged increased vigilance as more cases of Japanese encephalitis virus emerge across the eastern states, with the deluge of rain and widespread flooding adding to fears of wider transmission.

A woman in her 60s with the virus has been placed on life support at a Brisbane hospital after a camping trip through southern Queensland, the first locally acquired case of Japanese encephalitis in the state in 24 years.

Victorian health authorities are now aware of six suspected cases, aged from four months to 75 years, connected to a piggery near Echuca in the state’s north.

NSW Health confirmed a resident of the NSW-Victoria border region was considered a highly probable case of Japanese encephalitis and was in an intensive care unit in a stable condition.

Two other NSW residents, initially counted under Victorian statistics, have been confirmed as positive cases. Several more patients are undergoing further testing and more cases are expected to be confirmed in the coming days.

The virus has also been found in 14 piggeries across Queensland, NSW, Victoria, and, for the first time, South Australia.

Australia’s acting chief medical officer, Dr Sonya Bennett, has declared the unfolding outbreaks a “communicable disease incident of national significance” after briefing the national security committee of cabinet on the danger.

“A national working group of communicable disease, vaccine and arbovirus experts has been established to support the response, including mosquito surveillance and control measures and identification of those at direct risk, and for the rollout of vaccines,” said Dr Bennett.

Dr. Sonya Bennett

“The Australian government’s health and agriculture departments are working very closely with their state government counterparts to ensure a swift and co-ordinated response.”

Japanese encephalitis is a viral infection transmitted from mosquitoes to human beings.

Although fewer than 1 per cent of cases develop symptoms, Japanese encephalitis can cause severe brain and spinal cord infections, and sometimes death. Symptoms include headaches, seizures, sudden weakness and fever.

University of Sydney infectious diseases specialist Phillip Britton advised against undue panic, saying the risk of Japanese encephalitis could be minimised by taking simple precautions against mosquito bites. “The most important risk factor is exposure to the mosquitoes that could be carrying it – so people who (are) rurally exposed, go camping, particularly around water bodies,” said Professor Britton.

“But it is possible that an infected human, if they’re bitten by a mosquito, could be the source of the mosquito being infected.”

Professor Britton’s words echo the advice of NSW Health acting chief health officer Marianne Gale, who urged locals to reconsider outdoor activities, especially around rivers and waterways where mosquitoes breed.

“NSW Health is cautioning people undertaking outdoor activities such as camping and fishing to carefully consider their plans,” Dr Gale said.

“People should be particularly vigilant given the recent wet weather conditions, which have led to very high mosquito numbers that may increase further in the coming days and weeks.”

Professor Britton said that while it was unclear how the disease made it to the southeastern states, the increased wet weather and flooding events likely increased the risk of a “vector-borne infection like Japanese encephalitis” to thrive, as infectious disease researchers predicted.

“Given that this has been a predicted concern for some time, we have to conclude the effects of extreme weather events and particularly rain has been what has exposed Australia to the risk of this emerging here,” Professor Britton said.