The epidemiology of travel-associated shigellosis-regional risks, seasonality and serogroups

Objectives: To give a detailed risk estimate of contracting travel-associated shigellosis in various regions of the world. Methods: Data on notifications of travel-associated shigellosis in Sweden 1997-2003 were compared with information on recent travel abroad from a comprehensive database based on telephone interviews with more than 160 000 Swedish travellers. Results: From the national notification database 2678 patients with travel-associated shigellosis were retrieved. The highest risk of being notified with shigellosis was seen in returning travellers from India and neighbouring countries (318/100000 travellers), East Africa (219/100000), West Africa (120/100000), and North Africa (76/100000). Data on serogroup was available for 2529 isolates. Shigella sonnei was the most common serogroup (67%), followed by Shigella flexneri (26%), Shigella boydii (5%), and Shigella dysenteriae (3%). A higher risk was seen in children below the age of six, compared to older children and adults and in women compared to men. A distinct seasonal pattern was noted with the highest risk of shigellosis in July-October and the lowest in May. Conclusions: Denominator based data on reported travel-associated infections are well suited to give risk estimates per region of infection, that could be used to target high-risk groups for pre-travel advice. (c) 2005 The British Infection Society. Published by Elsevier Ltd. All rights reserved.