The H5N1 virus that infected a Canadian teen appears not to have spread, but it shows signs of mutation that makes flu virologists nervous.

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.

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 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.

Remember the H1N1 swine flu pandemic of 2009? Well, H5N1 bird flu could be next - H5N1 bird flu has infected more than 50 people across seven states, with cases steadily climbing