09 November 2020

Ross River virus risk expands from South West to the Midwest and Gascoyne

The Department of Health is urging residents and travellers throughout Western Australia (WA), to take extra precautions to avoid mosquito bites over the coming months, to prevent mosquito-borne disease transmission.

The warning follows ongoing Ross River virus (RRV) detections in mosquitoes and a recent increase in the number of human cases of RRV disease notified to the Department of Health, indicating the virus is very active in the environment.

The current risk of acquiring RRV is highest in the South West of WA, and along the coastal Midwest and Gascoyne regions, from Jurien Bay to Denham.

Acting Managing Scientist at the Department of Health, Dr Abbey Potter, said that the increased activity is likely to be the result of prevailing ‘La Niña’ weather conditions, coupled with a number of years of below average RRV activity in WA.

“RRV naturally cycles in the environment between mosquitoes and animal hosts, such as kangaroos. During an outbreak, infected animals develop immunity to the virus, reducing the potential for transmission in subsequent years,” she said.

“We have now experienced a number of years of below-average activity of RRV, so it is reasonable to expect that fewer animal hosts are immune at the moment. When low herd immunity is coupled with large numbers of mosquitoes and sustained virus activity, we can expect to see an increase in the number of cases of RRV disease in people.”

“Recent rainfall and increased tidal activity, combined with warm weather, is likely to result in a continuation of high mosquito numbers over coming weeks.”

“Mosquito management is being undertaken by local government authorities in collaboration with the Department of Health in areas with a recognised risk of RRV activity,” she said.

“However, it is not realistic to rely on mosquito management programs alone to control all mosquitoes. Individuals living in or travelling to the regions need to take their own precautions to avoid mosquito bites.”

Symptoms of RRV disease can last for weeks to months, and include painful or swollen joints, sore muscles, skin rash, fever, fatigue and headaches. The only way to diagnose the disease is by visiting your doctor and having a specific blood test.

There is currently no vaccine or specific treatment for RRV disease, the only way to prevent infection is to avoid being bitten by mosquitoes.

Despite the warning, there is no need to alter any travel plans. Individuals living or travelling in the regions are encouraged to take the following precautions to prevent mosquito bites:

  • avoid outdoor exposure, particularly at dawn and early evening;
  • wear protective (long, loose-fitting, light-coloured) clothing when outdoors;
  • apply an effective personal repellent containing diethyltoluamide (DEET) or picaridin evenly to all areas of exposed skin and always follow the label instructions;
  • ensure infants and children are adequately protected against mosquito bites, preferably with suitable clothing, bed nets or other forms of insect screening;
  • remove water holding containers from around the home and garden to ensure mosquitoes do not breed in your own backyard;
  • use mosquito coils and mosquito lanterns and apply barrier sprays containing bifenthrin in patio and outdoor areas around houses; and
  • ensure insect screens are installed and in good condition on houses and caravans;
  • use mosquito nets and mosquito-proof tents if sleeping outside.

For more information about mosquito prevention visit:



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