West Nile virus
What is West Nile virus?
West Nile virus (WNV), also known as West Nile Fever, affects birds, horses and humans. It was discovered in the West Niledistrict of Uganda in 1937. WNV is commonly found in Eastern Europe, Africa, West Asia and the Middle East. It was reported for the first time in North America in 1999 and in Canada in 2001. It may have come to North America with international passengers, imported birds and mosquitoes, or migration of infected birds.
In the U.S., different ways of transmission have emerged since 2002. One case involved transplacental (mother-to-fetus) transmission and one case involved transmission of the WNV through breast milk. In 2003, there were a few cases of WNV transmission through organ transplants and blood transfusions. At present, the risk of WNV spread through these methods is very low.
Can West Nile virus be spread through food?
There is no evidence that people can be infected with the WNV from eating infected birds or animals. It is still important to follow good food safety practices when preparing food and to eat thoroughly cooked meat.
Wild game hunters should use standard health and safety practices when they handle, clean or cook wild game. Gloves should be worn to prevent direct contact with animal blood and game should be thoroughly cooked before it is eaten.
How is West Nile virus spread?
The virus is not spread by person-to-person contact. Mosquitoes become infected by biting an infected bird. In turn, animals and human are infected by bites of infected mosquitoes. The virus is not spread by touching an infected person, coughing, sneezing or drinking from a shared cup.
The risk of being bitten by an infected mosquito is low and the chances of becoming seriously ill are even lower. Yet, anyone exposed to mosquitoes in an area where the WNV is present can become infected. Most people infected with this virus have no symptoms or present only very mild, flu-like symptoms such as fever, headache and body aches. People with weak immune systems are at greater risk of developing serious diseases such as meningitis and encephalitis. Meningitis is an inflammation of the membranes covering the brain and spinal cord. Encephalitis is the inflammation of the brain itself. These conditions can be fatal.
What can you do to control or prevent WNV infections?
Use an insect repellent and wear light-coloured long-sleeved shirts, long pants and a hat to avoid mosquito bites and to protect yourself and family members from WNV. Also, limit the areas around your home where mosquitoes can breed. To do this, drain water from items like pool covers, saucers under flower pots, recycle bins, garbage cans, etc.
Cases of animals infecting other animals or people have not been noted. However, one should follow standard safety practices when handling dead birds or animals; wear protective gloves and a mask, and cover any open wounds.
Animals like cattle, horses, dogs, sheep, cats, and squirrels can become infected with WNV. These animals are not major sources of infection for mosquitoes because they carry very little virus in their blood.
Information Sources
Canadian Food Inspection Agency. (2007). West Nile virus. Retrieved from,http://www.inspection.gc.ca/english/anima/heasan/disemala/wnvvno/wnvfse.shtml New link: http://www.inspection.gc.ca/animals/terrestrial-animals/diseases/immediately-notifiable/west-nile-virus/eng/1305840783267/1305840912854
Centers for Disease Control and Prevention. (2006). West Nile Virus: What you need to know. Retrieved from, http://www.cdc.gov/ncidod/dvbid/westnile/wnv_factsheet.htm
Health Canada. (2006). Its Your Health: West Nile virus. Retrieved from, http://www.hc-sc.gc.ca/iyh-vsv/diseases-maladies/wnv-vno_e.html
Kilpatrick, A.M., Kramer, L.D., Jones, M.J., Marra, P.P. & Daszak, P. (2006). West Nile Virus Epidemics in North America Are Driven by Shifts in Mosquito Feeding Behavior. PLoS Biol 4(4): e82. Available at: http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.0040082
Ontario Ministry of Health and Long-Term Care. (2008). Public health information: West Nilevirus. Retrieved from,http://www.health.gov.on.ca/english/public/program/pubhealth/westnile/wnv_mn.html
Public Health Agency of Canada. (2006). West Nile virus & animals. Retrieved from,http://www.phac-aspc.gc.ca/wn-no/anim_e.html
Date modified: 2012-07-31