Another Queenslander has tested positive to the mosquito-borne Japanese encephalitis virus and two others have been identified as suspected cases.
So far, 20 Australians have been confirmed as having the virus since it was detected in animals at piggeries across Victoria, NSW, South Australia and Queensland earlier this year.
Currently, 12 people across the four states are listed as probable cases — based on their symptoms and laboratory evidence that is "strongly indicative" of Japanese encephalitis — but medical experts cannot rule out other closely related mosquito-borne diseases, such as Murray Valley encephalitis.
NSW has eight confirmed cases, Victoria has seven, South Australia three and Queensland two.
Three people have died during the largest known outbreak of the virus in Australia: one in NSW, one in Victoria and another in South Australia.
When contacted yesterday, Queensland Health provided no details on the conditions of the state's two confirmed and two suspected infections.
Griffith University infectious disease expert Nigel McMillan said it was "gobsmacking" to see Japanese encephalitis virus had spread as far south as South Australia for the first time.
"South Australia and Victoria, they've never had that virus down there, ever, and NSW. These are geographically huge spreads," Professor McMillan said.
"To have it go so far is unexpected. Somewhere along the line our surveillance has gone awry."
The Queensland cases are the first locally acquired Japanese encephalitis infections in humans diagnosed in the Sunshine State since 1998.
Australia's acting Chief Medical Officer, Sonya Bennett, declared the Japanese encephalitis virus outbreak a communicable disease incident of national significance on March 4.
Japanese encephalitis virus not spread human to human
A national working group has been established to advise on mosquito surveillance and control measures, to identify people at greatest risk and to guide the targeted rollout of Japanese encephalitis virus vaccines.
Queensland pig owners have been urged to be alert for signs of Japanese encephalitis in their animals following confirmation of the disease at two piggeries in the state.
Professor McMillan said stillborn litters of piglets were a tell-tale sign.
However, Biosecurity Queensland has stressed that Japanese encephalitis is not a food safety concern. Pork remains safe to consume.
The virus is transmitted to people and animals — primarily pigs, horses and migratory birds — through mosquito bites. It cannot be transmitted directly from human to human nor from animal to human.
It is generally harmless in humans but, in less than 1 per cent of cases, people can develop potentially deadly encephalitis, an inflammation of the brain, and experience symptoms including neck stiffness, severe headache and coma.
'Public awareness is critical'
Griffith University virologist Lara Herrero said a third of those who developed neurological complications died and another 50 per cent developed long-term neurological disability.
"Japanese encephalitis causes roughly 15,000 deaths a year, globally, and, at this stage, there are no specific treatments for those who get the neurological disease manifestations," Dr Herrero said.
"Public awareness is critical in terms of understanding the risks. Without the bite of an infected mosquito, you can't contract this. Environment knowledge is critical, as is prevention.
"You don't want to get infected in the first place."
Dr Herrero said the recent south-east Queensland floods — combined with ongoing warm, humid weather — had created the ideal breeding conditions for mosquitoes.
She urged home owners to ensure they tipped out any stagnant water around their homes to reduce the potential for mosquitoes to breed.
People should also:
- avoid the outdoors when mosquitoes are most active, especially at dusk and dawn
- regularly apply insect repellent containing diethyl toluamide (DEET) when outside
- wear loose, light-coloured clothing to cover exposed skin.
The emergency doctor called for more research funding to allow scientists to find effective treatments for encephalitis.
