TORONTO - The agency responsible for most of Canada's blood supply says people who have travelled outside of Canada, the continental United States and Europe will be ineligible to give blood for 21 days after their return.

Canadian Blood Services says it is implementing the waiting period to mitigate the risk of the Zika virus entering the Canadian blood supply.

In a release Wednesday, Canadian Blood Services says the new waiting period is being implemented across the country and will take full effect in all of its clinics starting on Feb. 5.

Quebec's blood operator, Hema-Quebec, will be implementing the same change as of this Sunday.

Canadian Blood Services says the 21-day period ensures enough time has passed for the virus to be eliminated from a person's bloodstream, but it is asking people to postpone blood donation for at least a month after returning from travel outside the specified zones.

The three-week waiting period also applies to cord blood and stem cell donors who have travelled to affected areas. The waiting period begins the day a person returns to Canada.