Department of Health

Health warning on Ross River virus, Barmah Forest virus and other mosquito-borne diseases

Health advisory

Status:
Active
Advisory number:
221229
Date issued:
28 Dec 2022 - Update to Advisory issued 8 December 2022
Issued by:
Associate Professor Deborah Friedman, Deputy Chief Health Officer (Communicable Disease)
Issued to:
Health professionals and the Victorian community living in or travelling to rural or regional Victoria

Key messages

  • Victorians are advised to protect themselves against mosquito-borne diseases such as Ross River virus infection and Barmah Forest virus infection this summer.
  • Mosquito numbers of species known to transmit diseases are increasing.
  • Ross River virus and Barmah Forest virus detections in mosquitoes in rural and regional Victoria are increasing. 
  • Symptoms of Ross River virus infection and Barmah Forest virus infection can include fever, chills, headache, rash, joint pain and stiffness, muscle pain and fatigue. 
  • Clinicians should consider the possibility of mosquito-borne diseases in patients presenting with a compatible illness, especially those who live in or have travelled to rural or regional Victoria. 
  • A blood test early in the illness can indicate potential acute infection and should be repeated two weeks later for confirmation.
  • The most effective way to reduce your risk of mosquito-borne diseases is to avoid mosquito bites and remove mosquito breeding sites around your home.
  • For the most up to date viral detections in mosquitoes see the Department of Health webpage on mosquito-borne diseases.

What is the issue?

Recent weather conditions have been favourable for mosquito breeding across the state. Mosquito numbers are high across many parts of Victoria, and Ross River and Barmah Forest viruses have been detected repeatedly in trapped mosquitoes since November.  The risk of mosquito-borne diseases is likely to remain high this summer. Taking measures to avoid mosquito bites is critical to protect against infections.

Not all mosquitoes carry diseases – most are just a nuisance. However, some mosquitoes can carry a range of viruses that cause disease, including Ross River virus and Barmah Forest virus, and these mosquitoes are increasing in numbers. While endemic across most of the state, Ross River virus infection and Barmah Forest virus infection occur more frequently in inland riverine, floodplain and coastal areas and occasionally also occur in outer metropolitan areas.

More rarely, mosquitoes can carry Japanese encephalitis virus, Kunjin virus and Murray Valley encephalitis virus, which can cause serious illness. Aside from Japanese encephalitis, vaccines are not available for other mosquito-borne diseases. There is no vaccine currently available to protect against Ross River virus or Barmah Forest virus.

For the most up to date mosquito viral detections, see the Department of Health webpage on mosquito-borne diseases.

Symptoms and transmission

Ross River virus infection and Barmah Forest virus infection can cause fever, chills, headache, rash, joint swelling and pain, fatigue and muscle aches. Symptoms can persist for many months. It takes 3 to 10 days, and occasionally up to 21 days, for symptoms to occur after exposure. 

These infections are spread by infected mosquitoes and do not spread directly from person-to-person. 

Testing and notification

Clinicians should consider the possibility of mosquito-borne diseases in patients presenting with a compatible illness, especially people who live in or have travelled to rural or regional Victoria. A blood test early in the illness can indicate potential acute infection and should be repeated two weeks later for confirmation of mosquito-borne diseases.

Pathology services must notify mosquito-borne diseases to the Department of Health following diagnosis.

Treatment

Treatment is supportive. Rest is advised in the acute stages of Ross River virus infection and Barmah Forest virus infection. 

Prevention 

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

  • Cover up – wear long, loose-fitting, light-coloured clothing. 
  • Use mosquito repellents containing picaridin or DEET on all exposed skin.
  • Limit outdoor activity if lots of mosquitoes are about.
  • Remove stagnant water where mosquitoes can breed around your home or campsite.
  • On holidays make sure your accommodation is fitted with mosquito netting or screens.
  • Don’t forget the kids – always check the insect repellent label. On babies, you might need to spray or rub repellent on their clothes instead of their skin. Avoid applying repellent to the hands of babies or young children.
  • Use ‘knockdown’ fly sprays and plug-in repellent devices indoors.
  • Sleep under mosquito nets treated with insecticides if you don’t have insect screens on windows on your home or are sleeping in an untreated tent or out in the open.
  • Mosquito coils can be effective in small outdoor areas where you gather to sit or eat.

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Reviewed 29 December 2022

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