Influenza B virus is the only species in the genus Betainfluenzavirus in the virus family Orthomyxoviridae. Influenza B virus is only known to infect humans and seals with influenza.
Influenza B virus is the only species in the genus Betainfluenzavirus in the virus family Orthomyxoviridae. It is only known to infect humans and seals with influenza. This limited host range is apparently responsible for the lack of associated influenza pandemics in contrast with those caused by the morphologically similar influenza A virus as both mutate by both antigenic drift and reassortment.