Upgraded mosquito-borne disease risk in northern and central WA

The Department of Health upgraded the warning to people living and holidaying in northern and central Western Australia to take extra care to avoid mosquito bites. This warning follows widespread detection of the mosquito-borne Murray Valley encephalitis and Kunjin viruses and an increase in reports of people with Ross River virus and Barmah Forest virus diseases.

The Department of Health’s surveillance program (undertaken by The University of Western Australia) has detected widespread activity of Murray Valley encephalitis (MVE) virus and Kunjin virus in several locations in the Kimberley, Pilbara and Gascoyne regions. While there have been no confirmed MVE or Kunjin infections in people to date, infection with these viruses can cause very severe illness.

Department of Health Medical Entomologist Sue Harrington said recent rainfall and flooding in the northern half of the state had resulted in large numbers of mosquitoes that could be carrying these viruses.

“Murray Valley encephalitis virus and Kunjin virus are both carried by mosquitoes, and while the risk of being infected and becoming unwell is low, the illnesses can be severe and people should take sensible precautions to avoid mosquito bites,” Ms Harrington said.

“Initial symptoms of MVE include fever, drowsiness, headache, stiff neck, nausea and dizziness and people experiencing these symptoms should seek medical advice quickly. In severe cases, people may experience fits, lapse into a coma, and may be left with permanent brain damage or die,” she said.

“In young children, fever might be the only early sign, so parents should see their doctor if concerned, particularly if their child experiences drowsiness, floppiness, irritability, poor feeding, or general distress.

“Kunjin virus usually causes milder illness than MVE virus, but in rare cases, it also causes severe symptoms, including headache, neck stiffness, fever, delirium and coma.”

Ms Harrington said people most likely to be affected by Kunjin or MVE viruses were newcomers to affected regions, such as babies, young children, tourists or new employees, but anyone experiencing these symptoms should seek medical advice quickly.

In addition, a large number of cases of Ross River virus disease have been notified in people from the Kimberley and Pilbara regions. Cases of Barmah Forest virus disease are also being notified from the Midwest region. Large populations of mosquitoes in the Murchison region mean that people in this area are also at risk.

The illnesses caused by Ross River and Barmah Forest viruses are similar, with symptoms including painful joints, aching muscles, lethargy, fever, headache and skin rashes, and symptoms may last from days to months.

“There are no specific cures or vaccines for any of these mosquito-borne diseases so it is very important that people take care to prevent being bitten by mosquitoes.”

Ms Harrington said controlling mosquitoes in most rural regions of WA was generally not possible because of the large size and inaccessibility of natural mosquito breeding habitat.

People do not need to alter their plans to visit the Kimberley, Pilbara, Gascoyne, Murchison or Midwest regions, but it is important to avoid mosquito bites by taking a few simple steps, such as:

• Avoiding outdoor exposure from dusk and at night;
• Wearing protective (long, loose-fitting) clothing when outdoors;
• Applying a personal repellent containing diethyl toluamide (DEET) or picaridin to exposed skin or clothing. The most effective and long-lasting formulations are lotions or gels. Most natural or organic repellents are not as effective as DEET or picaridin or need to be reapplied more frequently;
• Ensuring insect screens are installed and completely mosquito-proof: use mosquito nets and mosquito-proof tents;
• Ensuring infants and children are adequately protected against mosquito bites, preferably with suitable clothing, bed nets or other forms of insect screening.

(Source: Western Australian Government Department of Health)