Australia has recorded its first confirmed death from Japanese encephalitis.
A man aged in his 60s from Victoria died from mosquito-borne JEV, an autopsy has found.
State health department officials said the man died on February 28 in northern Victoria.
Investigations are underway into how he contracted the virus.
The fast growing JEV outbreak has already caused hospitalisations of about 20 people around the nation with confirmed cases in Queensland, New South Wales and South Australia.
Some of those are seriously ill in intensive care.
South Australia health officials are still investigating the death of a local resident last month.
That fatality was among nine local cases of encephalitis, but they are yet to determine whether they are part of the JEV outbreak.
Along with the fast moving Japanese encephalitis are concerns from health experts on the rise of other serious mosquito infections.
In South Australia cases of Ross River Virus are on the rise as well, with 77 cases already in the state, compared with 48 cases at the same time last year.
More than 40 piggeries around the nation are also part of the JEV outbreak which targets pigs which "amplify" the virus.
Piggery workers have been declared at high risk of contracting the infection and have been selected for the first roll out of vaccines.
There is no treatment for JEV but it is one of the few mosquito viruses which has an effective vaccine.
Australia had a small stockpile of vaccines in case of an outbreak like this, and has already secured more supplies from Korea with more being sourced.
MORE READING: Outbreak a chilling reminder how close danger is.
The vaccine has also been recommended for transport workers or vets who visit pig farms and those who cull or hunt pigs.
After the confirmed Victorian death from JEV, health officials there are "urging caution" to northern Victorians, particularly those prone to severe illness such as older people and children under five..
JEV can cause inflammation of the brain - in around one per cent of cases who become infected, the health department said.
It can take days and weeks for the symptoms to develop such as a sudden onset of fever, headache, vomiting as well as seizures or disorientation.
People suffering these symptoms are urged to seek urgent medical attention.
"We strongly advise people take steps to limit their exposure to mosquitoes and avoid mosquito habitats such as stagnant water," a health department spokesman said.
Health officials are alarmed about the rise in mosquito numbers right across sodden areas of Australia, particularly along flooded areas of the east coast.
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