"CDC has sequenced the influenza viruses in specimens collected from the patient in Louisiana who was infected with, and became severely ill from #H5N1 virus.
The analysis identified low frequency mutations in the hemagglutinin gene of a sample sequenced from the patient, which were not found in virus sequences from poultry samples collected on the patient’s property...
...suggesting the changes emerged in the patient after infection."
https://www.cdc.gov/bird-flu/spotlights/h5n1-response-12232024.html