What are the different types of influenza viruses?
There are three types of influenza viruses: A, B and C. Virus A and B cause seasonal flu while C is typically associated with mild illness in children and young adults.
Influenza B and C virus have limited genetic diversity as both are restricted to a single specie each. Influenza type A virus has several sub-species. These species are classified on the basis of different combinations of hemaglutinin (HA) and neuraminidase (NA) — the proteins on its surface. For instance the H1N1 is an A type influenza virus that has an HA1 and an NA1 protein. Except H17N10, all known subtypes of influenza A virus can infect birds. The H17N10 virus is found in bats.