CDC identifies virus mutations in first critical US bird flu case

The United States Centers for Disease Control and Prevention (CDC) said on Thursday that its analysis of samples from the first severe case of bird flu in the country showed mutations that were not detected in samples from an infected backyard flock on the patient's property.

The patient, a Louisiana resident over the age of 65, was diagnosed last week with severe respiratory illness linked to the virus.

The patient was infected with the D1.1 genotype of the virus that was recently detected in wild birds and poultry in the US, and not the B3.13 genotype detected in dairy cows, human cases and some poultry in multiple states.

The CDC highlighted that the identified mutations are located in the hemagglutinin (HA) gene, which is crucial for the virus's ability to attach to host cells.

Despite the findings, the agency reassured the public that the overall risk from the outbreak remains low.

The mutations seen in the patient are rare but have been reported in some cases in other countries and most often during severe infections. 

One of the mutations was also seen in another severe case from British Columbia, Canada.

No transmission from the patient in Louisiana to other persons has been identified, said the CDC.