The Public Health Agency of Canada said Wednesday it's purchased 500,000 doses of a human vaccine to protect against avian influenza to protect people most at risk from being exposed to the virus by infected animals.

In other avian flu developments, tests at the US Department of Agriculture (USDA) have confirmed the H5N1 strain in rats for the first time, as the agency acknowledged that it was reversing recent layoffs of employees working on the avian flu response.

The Arizona Department of Agriculture (AZDA), in collaboration with the United States Department of Agriculture (USDA), has confirmed the first detection of H5N1 avian influenza in milk produced by a dairy herd in Maricopa County.

The Government of Canada has secured an initial supply of 500,000 doses of GSK's bird flu vaccine to protect individuals most at risk of being exposed to the virus through animals infected with avian influenza.

As bird flu cases continue to pop up in humans, Canada announced Wednesday that it purchased 500,000 doses of vaccine targeted at the virus. Here’s what you need to know about bird flu vaccinations in the U.