The H5N1 virus, or bird flu, has been discovered in dozens of dairy farms in the United States, and Canadian experts are urging monitoring on the northern side of the border.

Dr. Isaac Bogoch, an infectious disease specialist at the University of Toronto’s Health Network, said, "We need to actively look for it," noting that the number and diversity of mammals affected by the H5N1 virus this year have surged significantly.

Bogoch warns that "if more mammals become infected, it is clear that the virus can change and spread more easily among mammals."

Matthew Miller, of the McMaster Centre for Immunology Research in Hamilton, confirmed, "The mechanism that kept bird flu primarily in birds suddenly transferred to spread more easily in mammals, starting with dogs, cats, cattle, goats, and sea lions."

But does this mean it will inevitably spread widely among humans? “No, that is not inevitable.” “But I would say the risk is significant.”

Miller points out that no disease has caused more pandemics in recent history than influenza, citing the so-called Spanish flu pandemic of 1918, and the influenza epidemics of 1959, 1968, 1977, and more recently, the swine flu in 2009.

The recent outbreak in dairy farms in the United States has led to food inspections of ground beef and milk found in grocery stores, where the Food and Drug Administration discovered that one in five samples tested positive for H5N1 particles.

Bogoch notes that fragments of the virus are not capable of causing illness in humans.

However, in cats fed raw milk from American dairy farms, there was a high mortality rate, with more than 50 percent of the cats confirmed to have H5N1 dying from the virus.

Officials from the dairy industry in the United States and Canada state that pasteurization destroys pathogens in milk, urging consumers not to drink raw milk.