A New South Wales man has been admitted to hospital after becoming infected with the first transmission of Murray Valley encephalitis (MVE) in the state since 2011.
The new case follows the death of a Victorian woman her 60s from the virus early this month. She was the first recorded human case in Victoria since 1974.
NSW Health has confirmed a man in his 60s from the Riverina region has the virus.
He was potentially exposed to infected mosquitoes in the council areas of Temora, Edward River or Murrumbidgee and likely became infected in January.
The Victorian who died spent time in Buloke Shire and Swan Hill in the state's north-west during her acquisition period and probably became infected in early January.
The department says the man is receiving treatment in hospital and has confirmed it is the first case identified in the state this mosquito season.
MVE virus is spread to humans by infected mosquitoes and, in rare cases, can cause severe neurological illness.
Avoid mosquito bites: NSW Health
Director of NSW Health's One Health branch Keira Glasgow says the new infection is "significant" and "everyone in inland NSW" is being urged to take precautions.
She advises people in flood-impacted areas to focus on eliminating potential mosquito breeding grounds by emptying any water they can.
"There is no vaccination or specific treatment for Murray Valley encephalitis," she said.
"The best way to avoid infection is to avoid being bitten by mosquitoes, which are most active between dusk and dawn."
Mayor of the Murrumbidgee Council Ruth McRae says the recent flooding is influencing the volume of mosquitoes in the area.
"There's still a lot of water lying around and it is that time of the year that our waterways become large recreation areas," she said.
"All we can do is reinforce the message to cover up [and] watch what you're doing.
"Take the public health messaging seriously and don't take your finger off the pulse."
Severe illness rare
Only a small proportion of people infected with the MVE virus will experience symptoms, but Ms Glasgow says it can be fatal in some cases.
Symptoms can include fever, headache, nausea, vomiting, loss of appetite, diarrhoea and muscle aches.
Ms Glasgow says of the small number of infected people who develop symptoms, approximately half will develop the more serious infection.
She said the warning signs of a severe MVE infection could include "a severe headache, neck stiffness, a sensitivity to bright lights, drowsiness and confusion".
The virus had been detected in mosquitoes and sentinel chickens in western and southern NSW before the man became infected, Ms Glasgow said.
Using insect repellent can help with preventing mosquito bites, she said.
"For this particular type of mosquito the best repellents to use contain DEET or picaridin or oil of lemon eucalyptus," Ms Glasgow said.
"Make sure when you use repellent apply to all areas of exposed skin."
