A teenager in British Columbia has become the first person in Canada to test positive for the deadly H5N1 bird flu. Health authorities are urgently investigating how the virus spread, but they assure the public that the risk remains low.

British Columbia health officials have yet to identify a likely source of the infection, though none of the teen's contacts have tested positive for the virus so far.

A British Columbia teen who contracted Canada's first known human case of H5 bird flu has deteriorated swiftly in recent days and is now in critical condition, health officials reported Tuesday.

A Canadian teenager infected with bird flu — that country’s first case involving a locally acquired infection — is in critical condition and experiencing difficulty breathing, health officials said Tuesday.

A teenager in Canada is critically ill with the country's first human case of H5N1 bird flu. Health officials aren't sure how the youth was exposed.

Initial testing had indicated the teenager’s infection was from bird flu and was confirmed in further testing, the Public Health Agency of Canada said in a statement. The teen has been hospitalized in Vancouver since Friday and was reported in critical condition on Tuesday.