title: H1N1pdm in the Americas.
abstract: In late April 2009 the emergence of 2009 pandemic influenza A (H1N1pdm) virus was detected in humans. From its detection through July 18th, 2009, confirmed cases of H1N1pdm in the Americas were periodically reported to the Pan American Health Organization (PAHO) by member states. Because the Americas span much of the world's latitudes, this data provides an excellent opportunity to examine variation in H1N1pdm transmission by season. Using reports from PAHO member states from April 26th, 2009 through July 18th, 2009, we characterize the early spread of the H1N1 pandemic in the Americas. For a geographically representative sample of member states we estimate the reproductive number (R) of H1N1pdm over the reporting period. The association between these estimates and latitude, temperature, humidity and population age structure was estimated. Estimates of the peak reproductive number of H1N1pdm ranged from 1.3 (for Panama, Colombia) to 2.1 (for Chile). We found that reproductive number estimates were most associated with latitude in both univariate and multivariate analyses. To the extent that latitude is a proxy for seasonal changes in climate and behavior, this association suggests a strong seasonal component to H1N1pdm transmission. However, the reasons for this seasonality remain unclear.
authors.affiliation: Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, 615 N Wolfe St. Baltimore, MD 21205, USA. Electronic address: jlessler@jhsph.edu.
authors.forename: Justin
authors.initials: J
authors.lastname: Lessler
authors.affiliation: Pan-American Health Organization, 525 Twenty-third Street, N.W., Washington, DC 20037, USA. Electronic address: dossantt@paho.org.
authors.forename: Thais
authors.initials: T
authors.lastname: Dos Santos
authors.affiliation: Pan-American Health Organization, 525 Twenty-third Street, N.W., Washington, DC 20037, USA. Electronic address: aguilerx@paho.org.
authors.forename: Ximena
authors.initials: X
authors.lastname: Aguilera
authors.affiliation: Department of Biostatistics, Hopkins Bloomberg School of Public Health, 615 N Wolfe St. Baltimore, MD 21205, USA. Electronic address: rbrook@jhsph.edu.
authors.forename: Ron
authors.initials: R
authors.lastname: Brookmeyer
authors.affiliation: Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, 615 N Wolfe St. Baltimore, MD 21205, USA. Electronic address: dcumming@jhsph.edu.
authors.forename: Derek A T
authors.initials: DAT
authors.lastname: Cummings
mesh_terms: D002489:Central America / Q000453:epidemiology; D002980:Climate; D058872:Epidemics; D006801:Humans; D015994:Incidence; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000453:epidemiology* / Q000635:transmission / Q000821:virology; D009656:North America / Q000453:epidemiology; D012621:Seasons; D013020:South America / Q000453:epidemiology; D014481:United States / Q000453:epidemiology