close-up photo of mosquito on green background
close-up photo of mosquito on green background

Wet Weather Brings Japanese Encephalitis to Australia

Southern Australia has recorded its first-ever cases of the disease in an outbreak that has so far killed three people.

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Shawna Williams

Shawna joined The Scientist in 2017 and is now a senior editor and news director. She holds a bachelor's degree in biochemistry from Colorado College and a graduate certificate and science communication from the University of California, Santa Cruz.

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Apr 14, 2022

ABOVE: A Culex mosquito © ISTOCK.COM, doug4537

Severe floods that hit parts of eastern Australia earlier this year sowed death and millions of dollars of destruction. The heavy rainfall events also appear to have ushered in another unwanted effect: Japanese encephalitis. Normally confined to the tropics, the viral disease has now turned up in parts of Australia that have never experienced it before. So far the outbreak has affected at least 34 people and caused three deaths, The Washington Post reports. 

“With accelerating climate change, we’re going to be in a world of hurt,” Tim Inglis, the head of pathology and laboratory medicine at the University of Western Australia, tells the newspaper, “with some of these diseases that have in the past been restricted in the tropics extending, as we’re beginning to see.” 

See “Flooding and Storms Wreak Havoc for Australian Scientists” 

February and March saw record flooding along Australia’s northeastern coast, bringing standing water that Culex mosquitoes, which carry the Japanese encephalitis virus, need to reproduce and attracting migrating waterbirds that can also serve as carriers. “[M]igratory waterbirds are attracted to waterways and when that happens, they can bring viruses with them,” David Williams of the Australian Center for Disease Preparedness explains to Voice of America. Cases of the disease began to spread among farmed pigs even beyond the flooded areas, in Queensland, Victoria, New South Wales, and South Australia, and then doctors detected the virus in people. 

According to the US Centers for Disease Control and Prevention, most people infected with Japanese encephalitis are asymptomatic or experience only mild symptoms. A small percentage develop brain swelling—encephalitis—that can be fatal.  

In Australia, the virus had previously only cropped up in the country’s far north, and had not been detected on the mainland since 2004, according to The Conversation. The Australian Broadcasting Corporation reports that to contain the current outbreak, the government is purchasing 130,000 doses of a vaccine, which will be offered free of charge to high risk individuals, such as workers on pig farms. 

Japanese encephalitis is likely “here to stay” in Australia, Gregor Devine of QIMR Berghofer Medical Research Institute in Brisbane tells New Scientist. “Sometimes it will be unseen and sometimes it will spill over [into humans], but it’s not going to disappear.” In general, thanks to climate change, “We’re going to see more mosquito-borne diseases,” virologist Roy Hall of the University of Queensland in Brisbane tells the publication. “Exactly where, exactly when, we don’t know, but it will happen.”