Recently published research suggests as many as 750,000 Australians could be exposed to the mosquito-borne disease, typically dominant in Asia and rare for large parts of Australia.
The virus may become endemic in Australia amid rising temperatures and incessant flooding in various parts of the country, researchers from Brisbane’s QIMR Berghofer Medical Research Institute said.
The research paper was published in the scientific journal Clinical Infectious Diseases and warned that anyone living within 4km of an infected piggery is potentially at risk.
This is because the mosquito associated with the disease can fly several kilometres and pigs are believed to be a major amplifier of the virus, risking humans living nearby. People living close to populations of wading birds may also be at risk.
The study was carried out based on piggery distributions and the human population, and concluded that up to three per cent of the population, or 740,546 people, could be at risk. However, it presents the worst-case scenario, researchers said.
“We are extremely concerned about further outbreaks of Japanese encephalitis in Australia because of this third consecutive La Niña this year,” the paper’s senior author and head of the QIMR Berghofer Mosquito Control Laboratory, associate professor Greg Devine said.
“The wet and warm weather creates the right environment for mosquitoes to proliferate and may encourage changes in the distributions of the wild birds that maintain the virus during Australia’s winter months.”
He added that most Australians have not been exposed to the virus before, so have no immunity.
“We are urging people to take precautions. The best protection is vaccination, but currently, that’s not available to everyone. The next best protective measure is to avoid being bitten,” he said.
While Japanese encephalitis is rare in Australia, apart from some northern areas, there have been 31 confirmed human cases and six deaths in the country this year.
Last week, the Australian government’s health department said the outbreak “has been declared a Communicable Disease Incident of National Significance”.
According to local media, most cases are asymptomatic, but some people experience severe infections which can cause severe symptoms like convulsions, paralysis and coma.
The disease has proven to be deadly in other Asian countries with several deaths among children linked to the virus in countries like India every year.