USDA’s National Veterinary Services Laboratories (NVSL) has confirmed the full subtype for the highly pathogenic H7 avian influenza reported in Lincoln County, TN. The virus has been identified as North American wild bird lineage H7N9 HPAI based upon full genome sequence analysis of the samples at the NVSL. All eight gene segments of the virus are North American wild bird lineage. This is NOT the same as the China H7N9 virus that has impacted poultry and infected humans in Asia. While the subtype is the same as the China H7N9 lineage that emerged in 2013, this is a different virus and is genetically distinct from the China H7N9 lineage.
As additional background, avian influenza viruses are classified by a combination of two groups of proteins: hemagglutinin or “H” proteins, of which there are 16 (H1-H16), and neuraminidase or “N” proteins, of which there are 9 (N1-N9). Many different combinations of “H” and “N” proteins are possible. Each combination is considered a different subtype, and subtypes are further broken down into different strains. Genetically related strains within a subtype are referred to as lineage.