Department of Health

Health warning on mosquitoes and Ross River virus

Health advisory

Advisory number:
Date issued:
03 Jan 2017
Issued by:
Professor Charles Guest, Chief Health Officer, Victoria
Issued to:
Health professionals, aged care facilities, and the Victorian community

Key messages

  • Residents and visitors to Victoria are being warned to protect themselves against mosquito-borne diseases such as Ross River virus, Barmah Forest virus and Murray Valley encephalitis.
  • Ross River virus has now been detected in mosquitoes around Mildura and Moira / Barmah Forest, giving an early indication of increased risk of human disease for summer and early autumn.
  • The best protection from these diseases is to avoid mosquito bites - protective measures include regularly using mosquito repellent containing picaridin or DEET, wearing loose fitting clothing when outside and ensuring accommodation is mosquito proof.
  • A range of information relating to protecting against mosquito bites is available on the Beat the Bite campaign page on the Better Health Channel.
  • Doctors should consider the possibility of mosquito-borne disease in patients presenting with a compatible illness, especially after travel to rural or regional Victoria.
  • Notify Murray Valley encephalitis immediately on suspicion and Ross River and Barmah Forest virus after laboratory confirmation.

What is the issue?

Not all mosquitoes carry diseases – most are just a nuisance. Infected mosquitoes can carry a range of diseases including Ross River virus and Barmah Forest virus. These diseases can cause serious illness and occur regularly in regional Victoria. Murray Valley encephalitis is rare, but in a small percentage of infected persons it can cause serious illness including meningitis or encephalitis.

The summer holiday season is a time of increased outdoor activity, so taking measures to avoid mosquito bites is a critical step to protect against such diseases.

Who is at risk?

Anyone is potentially at risk of being bitten by mosquitoes and while most bites will only cause minor swelling and irritation, an infected mosquito can transmit potentially serious diseases. All parts of Victoria where there are mosquitoes may carry a risk for Ross River virus infection, although the risk is greatest in rural and regional Victoria. Infection appears to be rare in outer metropolitan areas.

Symptoms and transmission

Ross River virus and Barmah Forest virus disease are similar. Both can cause joint swelling and pain, fatigue and muscle aches which can persist for many months. A rash and fever may also develop. It takes three to nine days for symptoms of Ross River virus disease to occur after exposure, and occasionally up to 21 days. Barmah Forest virus disease symptoms occur between seven to ten days after a bite from an infected mosquito. While everyone recovers from the initial onset, symptoms may recur in some individuals for over a year or more.

Murray Valley encephalitis symptoms begin between seven to 28 days after exposure and include fever, headache, nausea and vomiting. This can lead to meningitis or encephalitis, which can lead to drowsiness, confusion, fitting, weariness or unsteadiness. In severe cases delirium and coma can follow, resulting in brain damage or death.


There are simple steps to protect against mosquito-borne diseases:

  • Wear long, loose fitting clothes if mosquitoes are around.
  • Use effective mosquito repellents containing DEET or picaridin on all exposed skin.
  • Try to limit outdoor activity if lots of mosquitoes are about. Dusk and dawn is when most mosquitoes are more active but some will also bite during the day.
  • Use ‘knockdown’ sprays and plug-in vaporising devices indoors.
  • Sleep under mosquito nets treated with insecticides if you don’t have flywire screens on windows.
  • Mosquito coils can be effective in small outdoor protected areas.

More information

Clinical information: Department of Heatlh and Human Services disease information and advice

Consumer information: Beat the Bite campaign on the Better Health Channel


Order Beat the Bite resources online or email  


Professor Charles Guest
Chief Health Officer

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Reviewed 03 January 2017


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