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 teenager in British Columbia, Canada has been hospitalized with a presumed case of H5N1 bird flu, the first detected human case in the country in the current outbreak.

A teenager in Canada, hospitalized with the country's first case of the H5N1 bird flu, is in critical condition. Health officials report his condition deteriorated rapidly despite having no prior health issues.