Salmonellosis and charter tourism: epidemiology and trends of imported human cases to Norway from the Canary Islands and Thailand, 1994-2008.

More than 70% of reported human Salmonella infections in Norway are infected abroad. The Canary Islands and Thailand are two of the most popular charter tourist destinations for Norwegians. Using surveillance data for the years 1994-2008, and denominator data on travel to the Canary Islands 2000-2008 and to Thailand 1997-2008, we present the epidemiology and trends of Salmonella infections in Norwegian tourists to these destinations. We found a declining trend in risk of salmonellosis in tourists returning from the Canary Islands, and a change in serovar distribution in travellers to Thailand with more S. Enteritidis infections, similar to that observed in Western European countries. The use of denominator data is important when studying risk of travel-related disease, as surveillance data tend to reflect travel activity more than the risk. Infections among tourists do not always affect the local residents and therefore may not be detected by local public health authorities. Sharing knowledge on the epidemiology of infections in tourists could be useful for observation of changes in trends in the countries visited, and in future outbreak investigations.