title: International travelers as sentinels for sustained influenza transmission during the 2009 influenza A(H1N1)pdm09 pandemic.
abstract: BACKGROUND
  International travelers were at risk of acquiring influenza A(H1N1)pdm09 (H1N1pdm09) virus infection during travel and importing the virus to their home or other countries.
  
  
  METHODS
  Characteristics of travelers reported to the GeoSentinel Surveillance Network who carried H1N1pdm09 influenza virus across international borders into a receiving country from April 1, 2009, through October 24, 2009, are described. The relationship between the detection of H1N1pdm09 in travelers and the level of H1N1pdm09 transmission in the exposure country as defined by pandemic intervals was examined using analysis of variance (anova).
  
  
  RESULTS
  Among the 203 (189 confirmed; 14 probable) H1N1pdm09 case-travelers identified, 56% were male; a majority, 60%, traveled for tourism; and 20% traveled for business. Paralleling age profiles in population-based studies only 13% of H1N1pdm09 case-travelers were older than 45 years. H1N1pdm09 case-travelers sought pre-travel medical advice less often (8%) than travelers with non-H1N1pdm09 unspecified respiratory illnesses (24%), and less often than travelers with nonrespiratory illnesses (43%; p < 0.0001). The number of days from first official H1N1pdm09 case reported by a country to WHO and the first GeoSentinel site report of a H1N1pdm09-exported case in a traveler originated from that country was inversely associated with each country's assigned pandemic interval, or local level of transmission intensity.
  
  
  CONCLUSIONS
  Detection of travel-related cases appeared to be a reliable indicator of sustained influenza transmission within the exposure country and may aid planning for targeted surveillance, interventions, and quarantine protocols.
authors.affiliation: Division of Global Migration and Quarantine, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Xiaohong M
authors.initials: XM
authors.lastname: Davis
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Hay
authors.forename: D Adam
authors.initials: DA
authors.lastname: Plier
authors.forename: Sandra S
authors.initials: SS
authors.lastname: Chaves
authors.forename: Poh Lian
authors.initials: PL
authors.lastname: Lim
authors.forename: Eric
authors.initials: E
authors.lastname: Caumes
authors.forename: Francesco
authors.initials: F
authors.lastname: Castelli
authors.forename: Phyllis E
authors.initials: PE
authors.lastname: Kozarsky
authors.forename: Martin S
authors.initials: MS
authors.lastname: Cetron
authors.forename: David O
authors.initials: DO
authors.lastname: Freedman
mesh_terms: D018562:Disease Transmission, Infectious / Q000517:prevention & control / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology / Q000503:physiopathology / Q000635:transmission / Q000821:virology; D038622:Internationality; D008297:Male; D008875:Middle Aged; D058873:Pandemics / Q000517:prevention & control / Q000706:statistics & numerical data; D011790:Quarantine / Q000458:organization & administration; D012720:Severity of Illness Index; D014195:Travel