Attack rates of dengue fever in Swedish travellers.
BACKGROUND
Dengue is endemic in many countries visited by Swedish travellers. We aimed to determine the attack rate of dengue in Swedish travellers and analyse the trends over time and the geographical variation.


METHODS
We obtained the following data from the Swedish Institute for Communicable Disease Control for the y 1995-2010: number of Swedish residents with confirmed dengue, the country and year of infection. We also obtained registers on the Swedish annual air traveller arrivals to dengue endemic areas from the United Nations World Tourist Organization for the time period. We estimated attack rates with 95% confidence intervals (CI).


RESULTS
In total, 925 Swedish travellers with confirmed dengue were reported. We found an increasing trend over time for most destinations. The majority of the dengue cases were acquired in Thailand (492 out of 925 travellers; 53%), with an attack rate of 13.6 (95% CI 12.7, 14.4) per 100,000 travellers. However, the 2 highest attack rates per 100,000 travellers were found for Sri Lanka (45.3, 95% CI 34.3, 56.4) and Bangladesh (42.6, 95% CI 23.8, 61.5).


CONCLUSIONS
Information on attack rates in travellers is more helpful in guiding travel medicine practitioners than reports of absolute numbers, as the latter reflect travel preferences rather than the true risk. Although the majority of dengue infections in Swedish travellers were acquired in Thailand, the attack rates for dengue in travellers to Sri Lanka and Bangladesh were much higher. These data aid in refining information on the risk of dengue in travellers.
From the Department of Public Health and Clinical Medicine, Epidemiology and Global Health, Umeå University , Umeå , Sweden.
Joacim
J
Rocklöv
Wolfgang
W
Lohr
Marika
M
Hjertqvist
Annelies
A
Wilder-Smith
D000293:Adolescent; D000328:Adult; D000368:Aged; D001459:Bangladesh / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D003715:Dengue / Q000453:epidemiology*; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D013188:Sri Lanka / Q000453:epidemiology; D013548:Sweden / Q000453:epidemiology; D013785:Thailand / Q000453:epidemiology; D014195:Travel / Q000706:statistics & numerical data*; D057236:Travel Medicine; D055815:Young Adult
Dengue; Swedish travellers; attack rate; dengue importation; travel medicine; travellers