International travelers were at risk of acquiring influenza A(H1N1)pdm09 (H1N1pdm09) virus infection during travel to affected areas and importing see more the virus to their home or other countries.[1, 2] For example, a positive correlation was found between the volume of airline travelers

departing from Mexico and confirmed H1N1pdm09 imported cases identified in various countries during the early stage of the 2009 influenza pandemic.[3, 4] We investigated more broadly whether travelers can function as sentinels for sustained transmission in an affected country and could complement traditional surveillance systems and aid public health planning for targeted surveillance, interventions, and quarantine protocols at international borders. We describe the profile of travelers who carried H1N1pdm09 virus across international borders throughout the world and explore Z-VAD-FMK the relationship between detection of H1N1pdm09 in travelers and the level of H1N1pdm09 transmission in the exposure country[5] during the first phase of the H1N1pdm09 pandemic. The 49 GeoSentinel sites in six continents contributing data are specialized travel and tropical medicine clinics that systematically provide clinical information on all ill returning travelers, as described elsewhere (www.geosentinel.org).[6] Intake at the sites reflects a mixed population of patients requiring

tertiary care and self-referred patients. Some sites are restricted to outpatient care, and at no Carnitine palmitoyltransferase II site is practice limited to the care of ill travelers. The GeoSentinel data-collection protocol was reviewed by the institutional review board officer at the National Center for Emerging and Zoonotic Infectious Diseases

at the Centers for Disease Control and Prevention and classified as public health surveillance and not as human-subjects research requiring submission to institutional review boards. Cases were defined as travelers with confirmed or probable diagnoses of H1N1pdm09 reported to GeoSentinel from April 1, 2009, through October 24, 2009, when H1N1pdm09 virus transmission was well established worldwide.[7] Confirmed H1N1pdm09 cases required positive results by real-time reverse transcriptase-polymerase chain reaction (rRT-PCR). At GeoSentinel sites, testing uses the best national reference laboratories in the site country. In the context of the 2009 pandemic, testing was done by public health authorities in all countries. Probable cases were defined as those with positive rapid tests for influenza A in acquisition countries where the predominant circulating strain was H1N1pdm09 or those with acute respiratory illness with an epidemiologic link to an rRT-PCR-confirmed H1N1pdm09 case. Two separate groups of travelers who carried the infection across an international border are described.