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.

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.