Influenza pandemics of the 20th century.
Three worldwide (pandemic) outbreaks of influenza occurred in the 20th century: in 1918, 1957, and 1968. The latter 2 were in the era of modern virology and most thoroughly characterized. All 3 have been informally identified by their presumed sites of origin as Spanish, Asian, and Hong Kong influenza, respectively. They are now known to represent 3 different antigenic subtypes of influenza A virus: H1N1, H2N2, and H3N2, respectively. Not classified as true pandemics are 3 notable epidemics: a pseudopandemic in 1947 with low death rates, an epidemic in 1977 that was a pandemic in children, and an abortive epidemic of swine influenza in 1976 that was feared to have pandemic potential. Major influenza epidemics show no predictable periodicity or pattern, and all differ from one another. Evidence suggests that true pandemics with changes in hemagglutinin subtypes arise from genetic reassortment with animal influenza A viruses.
New York Medical College, Valhalla, New York, USA. ekilbourne@snet.net
Edwin D
ED
Kilbourne
D000818:Animals; D000956:Antigens, Viral / Q000235:genetics; D004196:Disease Outbreaks / Q000266:history*; D049673:History, 20th Century; D049674:History, 21st Century; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D009980:Influenza A virus / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity / Q000502:physiology; D007252:Influenza Vaccines / Q000276:immunology; D007251:Influenza, Human / Q000453:epidemiology* / Q000266:history* / Q000517:prevention & control; D009515:New Jersey / Q000453:epidemiology; D012426:Russia / Q000453:epidemiology; D013552:Swine / Q000821:virology
D000956:Antigens, Viral; D007252:Influenza Vaccines