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West Nile Virus (Information from The Fraser Health Authority)

What is West Nile Virus (WNV)?
What are the symptoms of WNV? 
How to Lower the Risk of Infection 
Should I Report Dead Birds This Year? 
How Will the Public Know if West Nile Virus Has Been Found in BC?
More Information

West Nile virus (WNV) is a disease spread to humans through the bite of an infected mosquito. The mosquitoes pick up the virus from feeding on infected birds. Not all mosquitoes or birds carry WNV. The types of birds that are most affected are corvids, which include crows, ravens and jays. The virus is named after a region in Uganda where it first appeared in 1937. From there, outbreaks were recorded in Europe before the first North American infection was confirmed in New York State in 1999. WNV has since been detected in most American states and Canadian provinces.

Typical West Nile virus transmission cycle

West Nile virus transmission cycle

Mosquitoes become infected when they feed on infected birds, which may circulate the virus in their blood for a few days. Infected mosquitoes can then transmit West Nile virus to humans and animals while biting to take blood. The virus is located in the mosquito's salivary glands. During blood feeding, the virus may be injected into the animal or human, where it may multiply, possibly causing illness.

Mosquito Life Cycle

Mosquito life cycle

Mosquitoes spend three of their four life stages in the water and any sources of standing water are potential mosquito breeding hot spots. It takes seven to ten days for a mosquito egg to hatch and grow into an adult mosquito. By removing any standing water around your home on a weekly basis, you will prevent new eggs from hatching.

A comprehensive approach has been developed by health officials to identify, as early as possible, the presence of the virus within the province through the testing of mosquitoes and dead birds. The mosquito season is generally from May until the first hard frost in late September- October.

What is West Nile Virus (WNV)? 
Infection from West Nile Virus is caused by a mosquito-borne virus that is normally passed between birds and mosquitoes. It is transmitted to humans through the bite of an infected mosquito. Transmission can also be through blood transfusions, donated organs, breast milk and in utero. At this time there is no specific vaccine, treatment or medication for WNV. Serious cases are managed with supportive measures to lessen symptoms and prevent secondary infections. Canadian Blood Services is currently working on the development of a screening test to be used on donated blood.

What are the symptoms of WNV?
Most people who have been infected will have no symptoms; some, (approximately 20%) will develop mild flu-like symptoms including fever, headache and muscle aches. A rash or swollen lymph glands may also be present. These symptoms usually last a week or less. In less than 1% of cases the virus may cause meningitis, (inflammation of the lining of the spinal cord and brain), or encephalitis, (inflammation of the brain). If severe headache or neck stiffness develops a physician should be consulted. The incubation period for the virus is from 2-15 days. People over the age of 50 are most at risk of becoming severely ill. The reason for this is not known.

How to Lower the Risk of Infection 
Not all mosquitoes carry the West Nile Virus, (less than 1%). The risk of infection is extremely small. Follow the FOUR D's to reduce the risk by preventing mosquitoes from biting and breeding:

  1. DRAIN your property of standing water, such as clogged gutters, saucers under plant pots, tarps, used tires. Change water in bird baths and wading pools frequently.
  2. DUSK/DAWN - take extra care; this is when mosquitoes are most active.
  3. DRESS appropriately by wearing baggy, long-sleeved shirts and pants, shoes and socks when outdoors, especially at dawn and dusk. Wear light-colour clothing since dark colours attract mosquitoes.
  4. DEFEND against mosquito bites by using mosquito repellants wisely.

In addition:

  • Avoid forested areas during the day.
  • Keep your yard mowed and bushes trimmed to prevent resting places for adult mosquitoes. Mosquitoes do not breed in grass and vegetation but they like to rest and hide there.
  • Garden ponds should have water pumps or other means of keeping the water moving.
  • Fish and birds in garden help tremendously on cutting back the presence of mosquitoes.
  • Do not overfeed your fish. Hungry fish make better mosquito predators.
  • Remove standing water: throw out, puncture, or fill old tires, tin cans, unused flower pots, and other junk that can collect water.
  • Empty bird baths weekly.
  • Cover water barrels with tight fitting lids or window screening.
  • Eavestroughs should be clean and free flowing.

Should I Report Dead Birds This Year? 
Yes. A fixed number of birds from each health authority will be tested for WNV as part of a provincial program of bird testing. If you find a dead crow, please call toll-free 1.888.WNV.LINE (1.888.968.5463). to find out if they need to test the bird for infection.

How Will the Public Know where West Nile Virus Has Been Found in BC?
The Fraser Health Authority will provide updates for the public on the results of testing for West Nile Virus in mosquitoes or crows within Fraser Health region. 

More Information:

 HealthLink BC HealthLink BC 
Information about symptoms
8-1-1 or
7-1-1 (hearing impaired)
 BC Centre for Disease Control BC Centre for Disease Control 
Background, presence in B.C., control strategies and prevention measures. Also has online section for reporting dead birds that you suspect may be potential carriers of WNv.
 Fraser Health Fraser Health Authority 
Provides health services for 20 municipalities ranging from Burnaby to White Rock to Hope. Gives information on symptoms, treatment, prevention, what private properties and residents can do to minimize the risk of WNV on their land and is the place to report dead crows or jays for collection.
1-888-WNv-LINE or
Last updated: 23/05/2012 9:46:19 AM