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 British Columbia was hospitalized in critical condition with the disease, and officials were working to find out how the person was exposed to the virus.

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. The teen's case was announced Saturday by provincial health officials,