The infection was likely acquired in January this year.
He may have also been exposed to infected mosquitoes in the Temora Shire or Murrumbidgee Council areas.
The Riverina infection is the first case of MVE in NSW this mosquito season, and the first confirmed transmission of the virus in the state since 2011.
The man has been admitted to hospital, where he continues to receive treatment.
NSW Health’s One Health branch director Keira Glasgow said the case follows recent MVE detections in mosquitoes and sentinel chickens in parts of western and southern NSW where surveillance is being carried out.
“There is no vaccination or specific treatment for Murray Valley encephalitis, so we urge the community to do everything they can to protect themselves against mosquito bites,” Ms Glasgow said.
“The best way to avoid infection is to avoid being bitten by mosquitoes, which are most active between dusk and dawn. Avoiding mosquito bites will also protect against other mosquito-borne infections including Japanese encephalitis, Kunjin and Barmah Forest viruses.
“Only a small proportion of people infected with the virus will have any symptoms, which include fever, headache, nausea, vomiting, loss of appetite, diarrhoea, and muscle aches.
“Signs of severe infection include severe headache, neck stiffness, sensitivity to bright lights, drowsiness, confusion, seizures, and loss of consciousness.”
Ms Glasgow said that the number of MVE detections in mosquitoes and sentinel chickens this season was concerning.
In response, NSW Health has established an expert advisory panel on mosquito control and management with medical entomologists from across Australia.
“We are looking closely at the various approaches to mosquito control in different environments and in areas with different population densities to help inform our approach to mosquito control and management in NSW,” Ms Glasgow said.
MVE virus is spread to humans by infected mosquitoes. Rarely, it causes severe neurological illness.
For further information and ways to protect yourself, go to www.health.nsw.gov.au/Infectious/mosquito-borne/Pages/default.aspx.
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