Bird flu virus shows mutations in first severe human infection in US, CDC says

Mutations are rare but have been reported in some cases in other countries and most often in extreme infections

The US Centers for Disease Control and Prevention said on Thursday its analysis of samples from the first severe case of bird flu in the country last week showed mutations not seen in samples from an infected backyard flock on the patient's property.

The CDC said the patient's sample showed mutations in the hemagglutinin (HA) gene, the part of the virus that plays a key role in it attaching to host cells.