title: Influenza epidemics in the United States, France, and Australia, 1972-1997.
abstract: Influenza epidemics occur once a year during the winter in temperate areas. Little is known about the similarities between epidemics at different locations. We have analyzed pneumonia and influenza deaths from 1972 to 1997 in the United States, France, and Australia to examine the correlation over space and time between the three countries. We found a high correlation in both areas between France and the United States (correlation in impact, Spearman's r= 0.76, p < 0.001, and test for synchrony in timing of epidemics, p < 0.001). We did not find a similar correlation between the United States and Australia or between France and Australia, when considering a systematic half-year lead or delay of influenza epidemics in Australia as compared with those in the United States or France. These results support a high correlation at the hemisphere level and suggest that the global interhemispheric circulation of epidemics follows an irregular pathway with recurrent changes in the leading hemisphere.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, Paris, France. viboudc@mail.nih.gov
authors.forename: Cécile
authors.initials: C
authors.lastname: Viboud
authors.forename: Pierre-Yves
authors.initials: PY
authors.lastname: Boëlle
authors.forename: Khashayar
authors.initials: K
authors.lastname: Pakdaman
authors.forename: Fabrice
authors.initials: F
authors.lastname: Carrat
authors.forename: Alain-Jacques
authors.initials: AJ
authors.lastname: Valleron
authors.forename: Antoine
authors.initials: A
authors.lastname: Flahault
mesh_terms: D001315:Australia / Q000453:epidemiology; D021821:Communicable Diseases, Emerging / Q000453:epidemiology* / Q000401:mortality; D004196:Disease Outbreaks; D005602:France / Q000453:epidemiology; D006801:Humans; D007251:Influenza, Human / Q000453:epidemiology* / Q000401:mortality; D011014:Pneumonia / Q000453:epidemiology* / Q000401:mortality; D012621:Seasons; D013997:Time Factors; D014481:United States / Q000453:epidemiology