Influenza in travellers.
OBJECTIVE
The importance of travelling as an important factor for spread of influenza has become even more evident during the recent pandemic year. All the same, the mechanism for seasonal spreading of influenza is not yet fully understood.


RESULTS
The incidence of influenza in returning febrile travellers from subtropical and tropical regions is between 5 and 15% with no significant differences between those vaccinated and not vaccinated in the reviewed studies. The power of the studies to detect differences are, however, low. In these studies, 12-85% of the travellers or pilgrims were vaccinated against influenza. Air transportation, and especially long-haul flight, is a key factor for the spread of influenza even though travel restrictions seem to be of no use for preventing a pandemic spread.


CONCLUSIONS
Influenza should always be considered in a febrile traveller with or without respiratory symptoms. Future studies on incidence of travel-related influenza should consider the short incubation period for a better estimate. Vaccine from the opposite hemisphere should be made available for travellers, and influenza vaccine studies should focus on optimizing the effect of the vaccine in the elderly and immunocompromised.
Askling
Helena H
HH
Karolinska Institute, Unit for Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden. helena.hervius-askling@karolinska.se
Rombo
Lars
L
D000401:Aircraft; D006801:Humans; D015994:Incidence; D007252:Influenza Vaccines / Q000276:immunology; D007251:Influenza, Human / Q000453:epidemiology* / Q000517:prevention & control / Q000635:transmission*; D013997:Time Factors; D014195:Travel; D014329:Tropical Climate; D014611:Vaccination / Q000706:statistics & numerical data
D007252:Influenza Vaccines