TORONTO — A teenager was hospitalized and in critical condition after contracting bird flu, in what Canadian officials said Tuesday was the country’s first known case of the virus being transmitted to a human.

Health officials in British Columbia were investigating how the teenager came down with the disease despite having no known links to poultry farms, the most common sites where bird flu has been detected in Canada.

The virus, called H5N1, is a low risk to the public, health officials said, because it does not spread easily between people. But prolonged outbreaks, such as a cluster in U.S. dairy cattle, can increase the chances of the virus mutating and spreading.

There have been 46 cases of people contracting the virus in the United States, according to the Centers for Disease Control and Prevention, nearly all of them farmworkers. Most cases have been mild.

About 36 people who came into contact with the young person in Canada have tested negative for the virus.

— The New York Times