27.12.2024

CDC has sequenced the influenza viruses in specimens collected from the patient in Louisiana who was infected with, and became severely ill from HPAI A(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. The patient was infected with A(H5N1) virus of the D1.1 genotype virus that is closely related to other D1.1 viruses recently detected in wild birds and poultry in the United States and in recent human cases in British Columbia, Canada, and Washington State. There were some low frequency changes in the hemagglutinin (HA) gene segment of one of the specimens that are rare in people but have been reported in previous cases of A(H5N1) in other countries and most often during severe infections. One of the changes found was also identified in a specimen collected from the human case with severe illness detected in British Columbia, Canada, suggesting they emerged during the clinical course as the virus replicated in the patient.
The mutation seen may result in increased virus binding to α2-6 cell receptors found in the upper respiratory tract of humans.