Template:Two other uses

Avian flu is any flu caused by a virus adapted to birds. It is also called bird flu, avian influenza and bird influenza.

The only known such viruses are Influenza A viruses. All subtypes (but not all strains of all subtypes) of this species are adapted to birds, so for many purposes avian flu virus is the Influenza A virus (the "A" does not stand for "avian").

As of 2006, "avian flu" is being commonly used to refer to the H5N1 subtype of Influenza A virus, the world's major flu pandemic threat.

"Avian flu", "bird flu", "avian influenza", and "bird influenza" all technically mean "flu from Influenza A viruses which is adapted to birds", but are commonly used to refer to these different things:

• flu:
  • flu from Influenza A viruses which is adapted to birds
  • the flu acquired from any Influenza A viruses
  • the H5N1 flu (flu acquired from H5N1)
• virus:
  • Influenza A viruses which are adapted to birds
  • the Influenza A viruses
  • the H5N1 subtype of the Influenza A virus.

"Flu" is short for "influenza". "Bird" or "avian" used as an adjective in front of either "flu or "influenza" mean exactly the same thing.

This means there are four ways of saying the same thing.

All four mean (1)a disease called a flu (2)from an infection from a virus adapted to birds (which includes no viruses other than Influenza A viruses, which includes all subtypes of Influenza A viruses, but does not include all strains of Influenza A viruses).

These four terms do not mean just any Influenza A virus flu as some Influenza A viruses have adapted to animals other than birds.

In technical contexts, correct useage of terms is necessary because precise distinctions are the essence of the communication.

• "Avian influenza strains are those well adapted to birds" ^[1]
• "An outbreak of influenza A (H5N1), also know as 'avian flu' or 'bird flu,' has been reported in several countries throughout Asia." Being known as is distinguished from actually being.^[2]
• "Avian influenza virus usually refers to influenza A viruses found chiefly in birds, but infections can occur in humans."^[3]
• "Of the few avian influenza viruses that have crossed the species barrier to infect humans, H5N1 has caused the largest number of cases of severe disease and death in humans. Unlike normal seasonal influenza, where infection causes only mild respiratory symptoms in most people, the disease caused by H5N1 follows an unusually aggressive clinical course, with rapid deterioration and high fatality." Seasonal influenza is human flu.^[4]
• "avian influenza HA bind alpha 2-3 sialic acid receptors while human influenza HA bind alpha 2-6 sialic acid receptors. Swine influenza viruses have the ability to bind both types of sialic acid receptors." ^[5]
• Sometimes a virus contains both avian adapted genes and human adapted genes. Both the H2N2 and H3N2 pandemic strains contained avian flu virus RNA segments. "While the pandemic human influenza viruses of 1957 (H2N2) and 1968 (H3N2) clearly arose through reassortment between human and avian viruses, the influenza virus causing the 'Spanish flu' in 1918 appears to be entirely derived from an avian source (Belshe 2005)." ^[6]

In nontechnical contexts, imprecise useage of terms is typical when discussing complex things.

• "According to the World Health Organization, avian flu, specifically the H5N1 strain, has been reported in birds, both wild and tame, in Asia, Europe, the Middle East and Africa since 2003." Here H5N1 is called a strain of "avian flu"; not distinguishing between a disease and a causitive agent of a disease.^[7]
• "A 1,000 square mile quarantine zone to combat an outbreak of bird flu was lifted in Scotland today - despite the spread of a similar disease south of the border." Here "bird flu" is used to mean "Asian lineage HPAI A(H5N1) flu" (which is a bird flu) and contrasted with flu from an avian adapted strain of H7N3 (which is also a bird flu). (Click the links for details.) ^[8]

• Dog flu
• Horse flu
• Human flu
• Swine flu