The epidemiology of travel-associated shigellosis— regional risks, seasonality and serogroups Karl Ekdahl a,b, * , Yvonne Andersson a a Department of Epidemiology, Swedish Institute for Infectious Disease Control (SMI), Stockholm, Sweden b Department of Medical Epidemiology and Biostatistics, Karolinska Institute, Stockholm, Sweden Accepted 1 February 2005 KEYWORDS Shigellosis; Travel; Diarrhoea; Risk factor; Age; Season Abstract 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 (318/100 000 travellers), East Africa (219/100 000), West Africa (120/100 000), and North Africa (76/100 000). 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. Q 2005 The British Infection Society. Published by Elsevier Ltd. All rights reserved. Introduction With increasing international travel the panorama of gastrointestinal infections in western countries is to a large extent affected by imported infections. Between 25 and 50% of the approx. 80 million people that each year travel to destinations in Africa, Asia, Pacific Islands, Latin America and remote areas of Eastern Europe, experience travellers diarrhoea. 1 About 80% of all episodes of travellers’ diarrhoea have a bacterial cause, and shigellosis belong to the top-five bacterial infections. 2,3 Shigellosis (bacillary dysentery) is a bacterial enteric disease caused by the four serogroups of the Journal of Infection (2005) 51, 222–229 www.elsevierhealth.com/journals/jinf 0163-4453/$30.00 Q 2005 The British Infection Society. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jinf.2005.02.002 * Corresponding author. Address: Department of Epidemiology, Swedish Institute for Infectious Disease Control (SMI), Stock- holm, Sweden. Tel.: C46 8 4572379; fax: C46 8 300626. E-mail address: karl.ekdahl@smi.ki.se (K. Ekdahl).