West Nile Virus
Date of Issue: May 13, 2003Hazard Summary
The West Nile virus has been identified in "corvid birds" (mainly crows) in Canada since 2001. While the risk of exposure to West Nile virus is low and the risk of serious health effects from the virus is even lower, it is important to know the symptoms and how to reduce your exposure.
Cause
West Nile virus is spread to humans through the bite of an infected mosquito. The mosquito becomes infected by feeding on the blood of a bird that carries the virus. Approximately two weeks must pass after a mosquito has fed on an infected bird, before it is capable of transmitting the virus.
The number of bird species that carry the virus is not known, but the groups that appear to be most affected include crows, blue-jays, gray jays, magpies and ravens. In Nova Scotia crows, jays and ravens are monitored.
Risk Factor and Protection
Workers at risk of exposure include those working outdoors when mosquitoes are actively biting - the risk being greatest from July to early September.
Occupations at risk include: farmers, foresters, landscapers and groundskeepers, construction workers, painters, roofers, pavers and other outdoor workers.
Contributing factors to the level of risk include working near stagnant water: pools, ponds, troughs, irrigation/drainage ditches, manure lagoons and equipment that allows water to collect and stand - tarps, wheel barrows, buckets, barrels, etc. Also the time of day may affect the risk of being bitten. Many mosquitoes bite people most actively at dusk and dawn.
Employers can help protect outdoor workers by:
- schedule work to avoid having workers outdoors when mosquitoes are most active and biting
- eliminate as many sources of standing water as possible
- turn over, cover, or remove equipment such as tarps, buckets, barrels and wheel barrows
- discard tires, buckets, cans and containers in the area
- place drain holes in containers that cannot be discarded
- fill in ruts and other areas that accumulate water
- change water every few days in animal drinking toughs or ponds
Workers can reduce their exposure by:
- wear long sleeved shirts, long pants and socks
- spray exposed skin with insect repellants (read and follow directions for repellant use)
- spray clothing with insect repellent products (do not apply repellent under clothing)
If you see a dead crow, jay or raven you can report the bird to the local office of the Department of Natural Resources (DNR), or call the DNR toll-free information line after hours at 1-800-565-2224.
Symptoms
Most people who become infected have no symptoms at all; however, some people may experience mild flu-like symptoms - fever, headache and body aches, develop a mild rash or swollen lymph glands.
Some people - seniors, young and those with weak immune systems - are at greater risk for serious health effects. These include meningitis or encephalitis.
Links to additional information
The following links provide greater detail on the virus.