The CDC's analysis revealed changes in the hemagglutinin (HA) gene, a critical component for the virus's ability to attach to host cells. The mutations "were not found in virus sequences from poultry samples collected on the patient's property, suggesting the changes emerged in the patient after infection," the CDC stated in its December 26 update.

One of the mutations was also seen in a sample from a British Columbia teenager who was hospitalized with bird flu, the CDC said. While the findings show that the virus has the capacity to mutate in ways that could make it more transmissible to humans ...