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West Nile Virus

Bayer Inc. does not guarantee the accuracy of the information contained in the West Nile Section provided herein or on any other sites. The information on this site should in no way be interpreted as medical advice. Should you require medical advice, please consult your healthcare practitioner.

Protection and symptoms

West Nile Virus is transferred from infected birds to people by the bite of a mosquito. The mosquito bites an infected bird and later bites a human, passing on the virus. Crows and a host of other birds can be infected. Although the main carriers of this disease are Culex mosquitoes, the virus has been found in most of the 20 or so kinds of mosquitoes that are commonly found in southern Canada.

As a Canadian with an active lifestyle, you should be aware of how you can prevent mosquito breeding on your property, how you can protect yourself from mosquito bites, and how you can recognize the symptoms of this disease.


Avoid outdoor activity during warm, humid evenings (especially for two hours before and after sunset) and on calm, cloudy days when mosquitoes are most active.

Don't make yourself an easy victim for hungry mosquitoes. Wear light-coloured, loose-fitting pants and a long-sleeved shirt or blouse when outdoors.

If outdoors, cover an infant carrier, carriage or playpen with mosquito netting.

If you must be outdoors when mosquitoes are active, treat exposed skin with a mosquito repellent. Read and follow all label directions and precautions carefully.


Although the chances of contracting West Nile Virus in Canada are relatively low, there is obviously some risk. Most people, even if infected, show no symptoms of this disease. They may have been infected and only had a brief fever or headache.

Symptoms of West Nile Virus infection may include fever, drowsiness, nausea, vomiting, headache, muscle weakness, rash and swollen lymph nodes.

If you have these symptoms, seek medical attention immediately. Your doctor can determine if you have this disease (or something with similar symptoms) and begin treatment if necessary.

To view Health Canada's West Nile Virus MONITOR, click here.

Health Canada also has an online resource available here.

About the Author: Dr. Roy Ellis, a well-respected Canadian entomologist, specializing in mosquito identification, surveillance and control, is a member of Health Canada's Subcommittee on Mosquito Surveillance and Control. Dr. Ellis has been involved with WNV in Canada since 1999 when Health Canada asked him to prepare a national response to this new disease. Since then, Dr. Ellis has helped to prepare contingency plans for mosquito control for Health Canada, Manitoba Health and the City of Winnipeg. Dr. Ellis has also prepared municipal mosquito control guidelines for cities and towns faced with WNV (sponsored by Health Canada).