Preparing for 2009 H1N1 Influenza

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Abstract
In 1743, when disease was presumed to be astral in origin, European newspapers reported on a contagious influence (influenza in Italian) that was being visited on the citizens of Rome. Two hundred years later, Wilson Smith and colleagues would isolate an influenza A virus, one of the members of the orthomyxovirus family.1 The key reservoirs of all influenza A viruses are migrating waterfowl, and intermittently, other hosts, such as pigs and people, are infected. Further classification of influenza A viruses is based on the specific hemagglutinin viral attachment spike and neuraminidase disengagement spike; the latter is cleaved when newly minted viruses emerge from infected cells. Smith's isolate was a variant of the H1N1 agent that caused the pandemic of 1918–1919, and H1N1 progeny persisted until the emergence of the Asian influenza pandemic strain (H2N2) in 1957. However, a new H1N1 strain of swine influenza emerged in 1976, and variants of this virus continue to circulate as one of the seasonal strains.