Abstract
To assess the attack and incidence rates for influenza virus infections, during October 2006–October 2007 we prospectively studied 1,190 adult short-term travelers from the Netherlands to tropical and subtropical countries. Participants donated blood samples before and after travel and kept a travel diary. The samples were serologically tested for the epidemic strains during the study period. The attack rate for all infections was 7% (86 travelers) and for influenza-like illness (ILI), 0.8%. The incidence rate for all infections was 8.9 per 100 person-months and for ILI, 0.9%. Risk factors for infection were birth in a non-Western country, age 55–64 years, and ILI. In 15 travelers with fever or ILI, influenza virus infection was serologically confirmed; 7 of these travelers were considered contagious or incubating the infection while traveling home. Given the large number of travelers to (sub)tropical countries, travel-related infection most likely contributes to importation and further influenza spread worldwide.
Highlights
To assess the attack and incidence rates for influenza virus infections, during October 2006–October 2007 we prospectively studied 1,190 adult short-term travelers from the Netherlands to tropical and subtropical countries
This prospective study with short-term travelers totropical countries supports earlier studies showing that influenza is 1 of the most frequently acquired infectious travel-related diseases [7]
Mutsch et al found an attack rates (ARs) for symptomatic infection of 0.9%; in our study, AR for confirmed influenza virus infection with fever was 2%, which is broadly similar to results of Mutsch et al comparing these 2 studies is difficult because of different study methods and circumstances
Summary
To assess the attack and incidence rates for influenza virus infections, during October 2006–October 2007 we prospectively studied 1,190 adult short-term travelers from the Netherlands to tropical and subtropical countries. Prospective studies estimate that up to 64% of short-term travelers experience an illness related to travel to (sub)tropical countries [3,4,5]. In these studies, respiratory tract infections were the second most frequent infectious disease contracted during travel, with attack rates (ARs) up to 26%; fever affected 11%–19.9% of travelers while they were abroad [3,4,5,6]. The destination of many short-term travelers, influenza virus circulates at low levels year-round [21,22]
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