Another cause for concern: flu season is underway in the U.S., and as seasonal influenza virus goes around, “humans, ourselves, could be a mixing vessel,” Davis says. If a person were simultaneously infected with bird flu and seasonal flu, the two viruses could theoretically combine to create a more transmissible strain.

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 teenager is hospitalized in critical condition with suspected bird flu, health officials reported 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 teenager picked up the virus, which has been detected recently in wild birds and poultry in the province,

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.