Avian influenza (bird flu)

• Avian influenza – better known as bird flu – is an infectious disease of birds caused by type A strains of the influenza virus. The disease was first identified in Italy more than 100 years ago. It occurs worldwide[i]

• Until mid-December 2003 however, avian flu was considered a rare disease with only 21 outbreaks amongst birds reported worldwide after 1959, most of them in Europe and the Americas

• Since 2003 a severe form of avian influenza – H5N1 – has affected poultry flocks and other birds in more than 50 countries

• Most recently, an outbreak of avian flu was reported at a turkey farm in East Anglia, England on 3 February 2007[ii]. This is the highly pathogenic Asian strain. It is similar to the virus that was found in Hungary in January 2007[iii]

• Avian flu was thought only to infect birds until the first human cases were found in Hong Kong in 1997[iv]

• In general there are three main groups of flu viruses (A, B and C). Influenza B and C viruses only infect people but influenza A viruses have the ability to cross the species barrier and infect people, birds, and animals such as pigs and horses

• Among people, influenza A is the source of ordinary flu epidemics and has caused all previous flu pandemics. Avian flu is caused by a subtype of influenza A: H5N1 virus[v]

• According to the World Health Organization (WHO), there is mounting evidence that the H5N1 strain has a unique capacity to jump the species barrier and cause severe disease, with high mortality, in people

• Humans can catch avian flu though close contact with live infected birds. Birds excrete the virus in their faeces, which dries and becomes pulverized, and is then inhaled[vi]

• There is no firm evidence that H5N1 has the ability to pass easily from person to person. But if it does acquire this characteristic, H5N1 could then spread widely and rapidly among people with the potential to cause another influenza pandemic

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