a disease of poultry and other birds caused by strains of *influenza A virus. The severity of the disease depends on the strain of virus involved: H5N1 is particularly deadly (causing fowl plague (or pest), with a mortality approaching 100%) and very contagious, being spread between domestic flocks by wild birds. This virus is not easily transmissible to humans, requiring close contact with infected birds or their faeces. The first human cases of H5N1 infection (‘bird flu’) were reported in 1997 and restricted to Hong Kong: 18 people were infected, six of whom died. Since then half of the people infected with H5N1 in Asia, Europe, the Near East, and Africa have died. Most cases of avian influenza in humans have resulted from contact with infected poultry; human-to-human transmission has been extremely rare. However, if H5N1 should develop this ability, a serious pandemic could occur. See also swine influenza.... avian influenza
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