Infection in other animals

Influenza infects many animal species, and transfer of viral strains between species can occur. Birds are thought to be the main animal reservoirs of influenza viruses. Sixteen forms of hemagglutinin and nine forms of neuraminidase have been identified. All known subtypes (HxNy) are found in birds, but many subtypes are endemic in humans, dogs, horses, and pigs; populations of camels, ferrets, cats, seals, mink, and whales also show evidence of prior infection or exposure to influenza.Variants of flu virus are sometimes named according to the species the strain is endemic in or adapted to. The main variants named using this convention are: Bird Flu, Human Flu, Swine Flu, Horse Flu and Dog Flu. (Cat flu generally refers to Feline viral rhinotracheitis or Feline calicivirus and not infection from an influenza virus.) In pigs, horses and dogs, influenza symptoms are similar to humans, with cough, fever and loss of appetite. The frequency of animal diseases are not as well-studied as human infection, but an outbreak of influenza in harbour seals caused approximately 500 seal deaths off the New England coast in 1979–1980. On the other hand, outbreaks in pigs are common and do not cause severe mortality.