Influenza A Subtypes and the Species Affected

Influenza A viruses are divided into subtypes based on two proteins on the surface of the virus: the hemagglutinin (H) and the neuraminidase (N). There are 18 different hemagglutinin subtypes and 11 different neuraminidase subtypes. All known subtypes of influenza A viruses have been found among birds, except subtype H17N10 and H18N11 which have only been found in bats. Below is a table showing the different hemagglutinin and neuraminidase subtypes and the species in which they have been detected.

Hemagglutinin

*These include seals, ferrets, minks, tigers, leopards, and polar bears, among others.

**Highly pathogenic avian influenza A(H5N1) viruses were first detected in pigs in Fujian Province, southern China in 2001. These infections in pigs in China – and, later, elsewhere in Asia — were caused by different A(H5N1) viruses than those that have caused outbreaks in wild birds, poultry, dairy cows, and other animals in the United States.

Neuraminidase