page_title: Global spread of H5N1
section_title: 1959–1997
hierarchical_section_title: Global spread of H5N1 / Timeline / 1959–1997
caption_attribution_description: English: Ducks Anas platyrhynchos in Plymouth, Massachusetts, United States. Deutsch: Stockenten in Plymouth, Massachusetts, Vereinigte Staaten Esperanto: platbekaj anasoj, en Plymouth, Massachusetts, Usono Taken with a Canon 5D and 70-200mm f/2.8L on December 30th, 2005.
context_page_description: The global spread of H5N1 influenza in birds is considered a significant pandemic threat. While other H5N1 influenza strains are known, they are significantly different on a genetic level from a recent, highly pathogenic, emergent strain of H5N1, which was able to achieve hitherto unprecedented global spread in 2008. The H5N1 strain is a fast-mutating, highly pathogenic avian influenza virus found in multiple bird species. It is both epizootic and panzootic. Unless otherwise indicated, "H5N1" in this timeline refers to the recent highly pathogenic strain of H5N1.
  Tens of millions of birds have died of H5N1 influenza and hundreds of millions of birds have been slaughtered and disposed of, to limit the spread of H5N1.
context_section_description: A highly pathogenic strain of H5N1 caused flu outbreaks with significant spread to numerous farms, resulting in great economic losses in 1959 in Scotland in chickens and in 1991 in England in turkeys. These strains were somewhat similar to the current pathogenic strain of H5N1 in two of its ten genes, the gene that causes it to be type H5 and the gene that causes it to be N1. The other genes can and have been reassorted from other subtypes of the bird flu species (their ease at exchanging genes is part of what makes them all one species). Evolution by reassortment of H5N1 from 1999 to 2002 created the Z genotype which became the dominant strain of highly pathogenic H5N1 in 2004 and is now spreading across the entire world in both wild and domestic birds.
  "The precursor of the H5N1 influenza virus that spread to humans in 1997 was first detected in Guangdong, China, in 1996, when it caused a moderate number of deaths in geese and attracted very little attention."
  In 1997, in Hong Kong, 18 humans were infected and 6 died in the first known case of H5N1 infecting humans.
  On December 28 to 29, 1997, 1.3 million chickens were killed by the government of Hong Kong. The government also suspended the import of chickens from mainland China.
caption: Ducks play a key role in H5N1 spread
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