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12 April 2011

Mosquito-borne disease risk intensifies in northern and central WA

Following confirmation of encephalitis in a Carnarvon resident the Department of Health has reiterated its warning to people living and holidaying in northern and central WA to take extra care against mosquito bites. It has been determined that the encephalitis was caused by Murray Valley encephalitis (MVE) virus or the closely-related Kunjin virus. In addition, several other possible cases of MVE infection are being investigated in Kimberley and Pilbara residents.

Department of Health Medical Entomologist Sue Harrington said that the Department's surveillance program (undertaken by The University of Western Australia) continued to detect activity of the rare, but potentially fatal, MVE and Kunjin viruses in many locations in the Kimberley, Pilbara and Gascoyne regions. There has also been an increase in reports of people with Ross River virus and Barmah Forest virus diseases in the northwest and the Midwest region.

"Murray Valley encephalitis virus and Kunjin virus are 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 that 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. 

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 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

Media contact: (08) 9222 4333

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