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West Nile Virus (WNV)

Since 2003, Canadian Blood Services has had an effective plan in place to deal with the threat of West Nile Virus (WNV). Our plan is purposely flexible so that we may respond to the magnitude and geographic spread of the WNV epidemic. In addition to testing every unit of blood, our plan includes other measures including deferring ill donors, withdrawing and destroying infected units, ongoing surveillance, and cancelling of blood donor clinics when necessary.

There is no risk of acquiring West Nile Virus by donating blood.

Blood donors are encouraged to continue donating as usual. The greatest risk to the blood supply is a shortage of blood. Canadian Blood Services particularly needs donors during the summer months to help build an inventory of tested products. To book an appointment to donate blood, please call us at 1 888 2 DONATE (1-888-236-6283).

Testing for WNV at Canadian Blood Services

2003 14
2004 0
2005 15
2006 8
2007 21
2008 1
2009 0
2010 0
2011 6
2012 17
2013 4*
*As of September 9, 2013
Single Unit Testing underway
in the following health region:
  • Saskatoon Health Region
  • Toronto Public Health Region
  • Halton, Hamilton-Wentworth, Niagara, Wellington-Dufferin-Guelph, Brant County and Waterloo Health Public regions
  • Ottawa Health Region
NOTE: This information is updated as required by Canadian Blood Services

WNV testing has been performed on every blood donation we have collected since July 2003. Testing can be performed either in mini-pools (six units are pooled prior to testing) or by single units (each individual unit is tested). Single-unit testing is believed to be able to identify extremely low levels of virus in blood donations from people who have just become infected.

Single unit testing will commence in a given health region when one positive donation is found through the mini-pool testing program or when recent human cases are identified in the population of a health region at a rate of greater than 1 in 1,000 in rural areas or greater than1 in 2,500 in urban areas. Pooled testing will continue on all donations where single unit testing is not being undertaken. Single unit testing will cease in the affected health region after seven days. If additional donations screen postive for the virus and/or the number of human cases in the health region is above the population trigger during that timeframe, the seven day period will recommence.

West Nile Virus testing was introduced in 2003. In every case where a donation tests positive for WNV through mini-pool or single unit testing, the infected donations are withdrawn and the donors are deferred from giving blood again for 56 days, after which time they are no longer contagious and are able to continue donating.

For more information on West Nile Virus and how to protect yourself and your family, please visit the Public Health Agency of Canada website at:

West Nile Virus (WNV)
WNV Action Plan
WNV Q & As
WNV Resources
WNV News Releases & Statements

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