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Reports about the spreading of West Nile virus, along with news of illness and death brought about by the virus, have made this a subject of concern. Those with OH&S responsibilities need to learn about West Nile virus (WNv), conduct hazard assessments, develop preventive measures and educate their workforce where a WNv threat exists. Here’s an introduction to get you on your way.
A Bit of History
West Nile virus was first detected in Uganda more than sixty years ago. Since then, it has been found in various locations around the globe. It wasn’t until 2001 that cases of WNv were first confirmed in Canada. Saskatchewan has had the largest number of WNv cases, but the virus has also been confirmed in Alberta, Manitoba and Ontario.
Medical / Biological Facts
Based on current medical and biological knowledge:
- West Nile virus is transmitted to humans when they’re bitten by infected mosquitoes. It’s believed that less than 1% of mosquitoes carry the virus.
- Most individuals with WNv infections experience only mild, fever-like symptoms or no symptoms at all. Some cases result in West Nile Fever or the more serious West Nile Neurological Syndrome.
- West Nile Fever can develop 3-14 days after infection. Symptoms include fever, nausea, vomiting and headache. This occurs in about 20% of infected individuals.
- West Nile Neurological Syndrome is much more severe. Patients develop encephalitis (inflammation of the brain) and/or meningitis (inflammation of the membranes that cover the brain and spinal cord). About 1-2% of WNv infected individuals develop this potentially fatal syndrome.
- Humans are not the only mammals susceptible to West Nile virus. Horses, donkeys and mules are also susceptible to WNv infection.
- The virus is carried by birds belonging to the Corvid family, which includes crows, jays, ravens and magpies.
- West Nile virus cannot be transmitted directly from a bird to a human.
Exposure Risk
Among the general population, persons over the age of 50 and those with a compromised immune system are most susceptible to the serious health effects of West Nile virus. Anyone at risk of being bitten by mosquitoes has some risk of becoming infected with WNv.
Workers most at risk include:
- outdoor workers who may be bitten by infected mosquitoes, and
- health care, veterinary and lab personnel who handle WNv-infected tissue or fluids.
Prevention
There are a number of things that individuals can do to prevent contracting West Nile virus. Avoiding mosquito bites is the key.
- Eliminate mosquito breeding sites (e.g., standing water) or avoid working near such areas.
- Where possible, avoid outdoor activities at dawn and at dusk – when mosquitoes are most active.
- Dress in light colours. Wear long sleeves, long pants and socks. Cover your head. Additional clothing will provide greater protection.
- Use an insect repellent that contains DEET (N,N-diethyl-m-toluamide) or a similar ingredient. Repellent should be applied to exposed, unbroken skin according to the manufacturer’s instructions. Maximum DEET concentration should be 30% when used by adults and 10% when used by children. The length of time that DEET is effective is related to its concentration:
- 6.5 hours for 30% DEET
- 5 hours for 15% DEET
- 3 hours for 10% DEET
- 2 hours for 5% DEET.
- Oil of lemon eucalyptus has been reported to be an effective alternative to DEET when 2 hours of protection or less is needed.
- Employers and occupational health & safety practitioners should educate their workforce about the hazards of West Nile virus and implement suitable exposure controls.
Where To Get More Information About West Nile Virus
There are many credible information sources to help you learn more about WNv and preventive measures. Health Canada and many provincial health ministries, as well as provincial occupational health & safety departments have developed educational materials about the West Nile threat. Here are a few resources to get you started:
Article Reproduced by Guzzardi & Associates With Permission. Copyright 2005 Escalade Services Group Inc.
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