Travelers are at risk of acquiring infectious diseases. Previous studies have estimated that about 11% of travelers develop fever during or shortly after their trip abroad. Influenza has been shown to be one of the most important cause of fever amongst travelers. A sero-epidemiological survey showed that 27 of 211 patients (12.8%) with fever during or after a trip abroad developed antibodies against the influenza virus. Another study showed that 13% of travellers, who consulted after return with flu-like symptoms, had PCR or culture-proven influenza. The incidence of influenza in travellers varies according to the seasons, but cases can be seen year round. In tropical countries transmission is year-long and in the southern hemisphere the flu epidemics occur during the summer of the northern hemisphere.