Naming Influenza Viruses

Influenza Viruses are classified by type. (A, B, or C) based on the proteins that make up the virus.  The type A virus is most commonly found in various kinds of animals including; ducks, chickens, pigs, Whales, and sometimes humans.

Type B most commonly circulates among humans, but can also be found in some animals as well.  Type C causes mild respiratory infections, but does not have the ability to cause widespread epidemics. 

Out of all three types of the influenza virus, Type A is the most dangerous.  Type A is thought to be the one that is responsible for the three most virulent global outbreaks of the influenza virus.  Type A influenza viruses are even further subcategorized into groups based on their specific surface proteins, HA and NA. So far scientists have found sixteen HA subcategories and nine NA subcategories of the Type A Influenza Virus.