Queensland has recorded its first locally acquired human case of mosquito-borne Japanese encephalitis in more than two decades.
It has been declared an issue of national significance, prompting warnings for people to take precautions against getting bitten by the insects, particularly as the state's south-east cleans up after the floods.
Here's what you need to know about the discovery of the case.
What do we know about the person who contracted the virus?
The woman is in her 60s and is in a critical condition on life support in Brisbane's Prince Charles Hospital after a camper van trip to southern Queensland.
Her diagnosis follows the recent detection of Japanese encephalitis in animal samples taken from a Goondiwindi commercial piggery, in the state's south.
The virus — which transmits through mosquito bites and not human-to-human contact or through eating pork — has also been found recently in piggeries in South Australia, Victoria and NSW, including one near the Queensland border at Tenterfield.
Earlier this week, four Victorians were diagnosed with the virus in what are believed to be the first cases recorded in southern Australia.
How serious is Japanese encephalitis?
Brisbane-based infectious disease physician Paul Griffin said while most people who developed Japanese encephalitis would only experience mild symptoms, in rare, severe cases, it could result in encephalitis — inflammation of the brain — which is potentially deadly.
Symptoms can include sudden onset of fever, vomiting, severe headache, neck stiffness and sensitivity to light.
"The main thing everyone needs to know is that not everyone who gets this virus ends up with severe encephalitis or the severe manifestations — in most people that's not the case," Dr Griffin said.
"It is something that we should take seriously enough to take some simple steps to reduce our chance of it being a big problem."
What precautions should be taken?
Dr Griffin, an associate professor at the University of Queensland, said people should take measures to prevent mosquito bites.
This includes the use of repellents containing diethyl toluamide (DEET) and through wearing closed-in shoes and loose, light-coloured clothing to cover arms and legs.
Is it related to the flooding?
No, but Dr Griffin said the timing of Japanese encephalitis being found in eastern Australia coinciding with a major flood event was "unfortunate", given the potential for increased mosquito breeding in the coming days.
"The virus has been there before these immense rainfall events and obviously it will be the right breeding ground for the mosquitoes now … so the timing is pretty terrible," Dr Griffin said.
"The usual things we say about having pooled water around households will become increasingly relevant as we start to get the bulk of the floodwater receded and a lot of the clean-up happening.
"If there's any residual water sources in pot plants or other small containers, make sure there's no pooled water anywhere that can facilitate the growth of mosquitoes."
What about vaccinations?
Australia's Acting Chief Medical Officer Sonya Bennett said earlier this week work was underway for targeted vaccinations to protect against Japanese encephalitis.
But Dr Griffin said a widespread vaccination campaign, such as the COVID-19 vaccine rollout, would not be necessary.
"It's more likely something we'd do on a particular risk basis and so people who work with pigs, in particular, would be highest on the list," he said.
What else is being done to stop more cases?
Queensland Health Minister Yvette D'Ath said she had spoken to local government leaders about spraying for mosquitoes in the coming weeks to reduce the risk of Japanese encephalitis.
The last locally acquired Queensland cases of Japanese encephalitis are believed to have occurred in 1998 — in a 12-year-old boy on Badu Island in the Torres Strait and a man working at the mouth of the Mitchell River at Cape York.
There were three cases notified in Queensland in 2019, but these were not locally acquired.
Is it spreading quickly?
On Friday afternoon, Dr Bennett declared the "unfolding situation" in Australia regarding Japanese encephalitis a "communicable disease incident of national significance".
She said the federal Health Department had become aware of cases of encephalitis of "unknown origin" in states other than Queensland that were being investigated, including for the possibility of Japanese encephalitis virus (JEV).
"The Australian government will work closely with states and territories to educate the community about JEV, what precautions people should take and symptoms to be aware of," Dr Bennett said.
"The government will also work closely with the states and territories to support the distribution of vaccine doses to at-risk population groups."
She said less than 1 per cent of people infected with JEV developed a serious illness.
Dr Bennett said a national working group of communicable disease, vaccine and arbovirus experts had been established to support the country's response to the virus, including mosquito surveillance and control measures, identification of those at direct risk and for the rollout of vaccines.
Australia's Chief Veterinary Officer Mark Schipp said JEV had been confirmed at 14 piggeries across NSW, South Australia, Queensland and Victoria.
"The key signs to look out for in pigs are stillborn or weak piglets. Piglets can develop encephalitis or wasting, depression or hind limb paralysis. Adult sows do not typically show signs of disease," he said.
"Pig producers are asked to be highly vigilant for signs of this disease and report unexplained pig abortions or stillbirths.
Horses can also develop JEV and may show signs of an elevated temperature, jaundice, lethargy or anorexia.
Other symptoms may include a lack of co-ordination, difficulty swallowing, impaired vision or over-excitement.
"Horse owners can also put measures in place to help their horses avoid mosquito bites, including using hooded rugs, fly masks, and applying a safe insect repellent," Dr Schipp said.
Pig and horse owners who suspect an animal is showing signs of JEV must report it to a local veterinarian or the national emergency animal disease watch hotline on 1800 675 888.
