Health officials were struggling to answer a broader and potentially worrisome question: how the infection occurred.

Cases of H5N1 bird flu in U.S. dairy and poultry workers have largely been mild. However, a new case in a British Columbia teenager has experts worried.

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 Canadian teen is hospitalized in critical condition with what is believed to be bird flu, a British Columbia health official said Tuesday. It’s not clear how the t

A teenager has been left in critical condition after contracting the first presumptive human case of avian influenza in Canada. Expert Sam Scarpino discusses the health risk and potential for spread.

A teenager is in critical condition in a British Columbia children’s hospital with what is likely Canada’s first human case of H5 bird flu

A Canadian teen is severely ill with what is believed to be bird flu. The teen is not known to have had any contact with infected animals.

Amid an ongoing outbreak of bird flu in American dairy herds and poultry flocks, Canadian officials have announced

H5N1 avian influenza, more commonly known as bird flu, has infected more than 100 million birds in the U.S. and almost 500 dairy cattle herds across 15 states. The virus has popped up in mammals including elephant seals,