These mozzies can kill you
How to protect yourself against the mosquitos spreading Japanese encephalitis.
Key Points
- Health professionals warn against the spread of Japanese encephalitis this summer.
- Australians have not been exposed to the virus before, so they have no immunity.
- Those who develop symptoms have a fatality rate of around 30 per cent.
Rain and mosquitos have always been linked to summer in Australia.
However, this year there is particular concern about an outbreak of the little-known mosquito-borne Japanese encephalitis virus (JEV). Its spread has been driven by a third consecutive La Nina, which is causing widespread flooding in the north of the country.
QIMR Berghofer researchers in Brisbane have used modelling to conclude that as many as 750,000 people could be at risk of exposure to the virus, which was confined to Asia and far northern Australia until last year.
JEV is maintained in wild birds and is spread to other animals, including pigs, humans, and horses, by mosquitoes. The virus dramatically expanded its range in Australia this year, as dozens of piggeries confirmed cases throughout southern Australia.
There were 31 confirmed human cases and six deaths in 2022, and it is feared JEV may now be endemic.
JEV safety tips:
- Check with your state health department to determine eligibility for vaccination.
- Protect yourself outside at dawn and dusk when mosquitoes are most active.
- Apply mosquito repellents containing Picaridin or DEET to exposed skin.
- Wear long, loose-fitting clothes that cover the arms, legs, and shoes that cover the feet.
- Install insect screens on doors and windows.
- Protect infants with mosquito-proof netting on prams.
- Use sprays and coils in small outdoor areas.
- Empty standing water that has collected around your home.
New wetlands have attracted infected water birds and provided breeding grounds for the common vector mosquito, Culex annulirostris. Feral pigs may also play a role in the transmission. In 2022, many tested positive for JEV in the Northern Territory and Queensland. The February 2022 outbreak was first detected in domestic piggeries across several states.
The researchers warn if piggeries become a focus for infection, anyone living within four kilometres of an infected piggery is potentially at risk as could be people living close to wading birds.
“Most Australians have not been exposed to the virus before, so they have no immunity,” Associate Professor Greg Devine, Group Leader of the Mosquito Control Laboratory said.
“The best protection is vaccination, but that is not available to everyone. The next best protective measure is to avoid being bitten by a mosquito,” he said.
However, only around one per cent of people who become infected show symptoms. But among those who develop symptoms, the fatality rate is around 30 per cent, and of those who survive, around half will have some long-term neurological damage.”
Symptoms range from fever to severe encephalitis (inflammation of the brain). There is no specific treatment for Japanese encephalitis, so doctors can only manage symptoms and provide support.
There are two highly effective and safe vaccines available in Australia, but supplies are limited, so health authorities are prioritising vaccination for high-risk groups.
Researchers are investigating viable solutions to the JEV vaccine shortage by reducing the dose required.
For more information, read the Fact Sheet about Japanese encephalitis.
