The Centers for Disease Control and Prevention has completed sequencing studies on viruses isolated from workers in contact with infected poultry in Nevada and Wyoming.  Genetic sequences have been posted on GISAID, an international database. 

The virus isolated from the Nevada patient was characterized as genotype D1.1 consistent with contact with dairy cows.  This virus demonstrated a mutation in the polymerase protein encoded by (D701N) that is associated with more efficient replication in mammalian cells.  A similar change was previously noted in a human case following contact with infected poultry in Chile in 2023.

The Wyoming patient was infected with H5N1 clade 2.3.4.4.b genotype D1.1.  This virus demonstrated a change designated E627K in encoding for polymerase. This mutation is associated with enhanced viral replication in mammals was noted in the initial human cases in Texas during March 2024.  Both viruses were demonstrated to be susceptible to current antiviral medications administered for influenza.