Post Reply - H2H-H5N1 spread in US

H5N1 is a subtype of Influenza A virus, like all subtypes it is an enveloped negative-sense RNA virus, with a segmented genome.^[36] Subtypes of IAV are defined by the combination of the antigenic hemagglutinin and neuraminidase proteins in the viral envelope. "H5N1" designates an IAV subtype that has a type 5 hemagglutinin (H) protein and a type-1 neuraminidase (N) protein.^[37] Further variations exist within the subtypes and can lead to very significant differences in the virus's ability to infect and cause disease, as well as to the severity of symptoms.^[38][39]

Influenza viruses have a relatively high mutation rate that is characteristic of RNA viruses.^[40] The segmentation of its genome facilitates genetic recombination by segment reassortment in hosts infected with two different strains of influenza viruses at the same time.^[41][42] Through a combination of mutation and genetic reassortment the virus can evolve to acquire new characteristics, enabling it to evade host immunity and occasionally to jump from one species of host to another.^[43][44]