Travellers returning to Sweden as sentinels for comparative disease incidence in other European countries, campylobacter and giardia infection as examples.

Comparable figures on disease incidence between countries are difficult to attain. We therefore compared risk of infection for Swedes going to other European countries. We took as the numerator the number of imported cases from European countries of campylobacter and giardia infection in the national Swedish surveillance database, and as the denominator, the number of visitors to each country from a commercial database on foreign travel. Risk of infection in tourists was also compared to national incidence figures for a selection of countries. During the 7 year period 1997-2003, 14,829 campylobacter and 1112 giardia infections were diagnosed in Swedes returning from a European country. The travel database contained information on 14,519 overnight trips to such a country during the same period. Risk of campylobacter infection was over 100 per 100,000 travellers to Portugal and Turkey, but only 1/100,000 in Finland. Risk of giardiasis was highest in Russia (50/100,000). There appears to be substantial underreporting of campylobacter infection in many European countries. In conclusion, the risk of infection with campylobacter and giardia varies 100-fold across Europe. Returning tourists as a sentinel population are a useful tool to estimate these differences. There are large--and unexplained--differences between the risk for travellers and reported national incidence.