Mortality following Campylobacter infection: a registry-based linkage study.

Background: Campylobacteriosis is one of the most commonly identified causes of bacterial diarrheal disease and a common cause of gastroenteritis in travellers from developed nations. Despite the widespread occurrence, there is little information on Campylobacter mortality.

Methods: Mortality among a cohort of Campylobacter cases were compared with the general population 0-1, 1-3, 3-12 and more than 12 month after the onset of the illness. The cases were sub-grouped according to if they had been infected domestically or abroad.

Results: The standardized mortality ratio for cases infected domestically was 2.9 (95% CI: 1.9-4.0) within the first month following the illness. The risk then gradually diminished and approached 1.0 after one year or more have passed since the illness. This initial excess risk was not attributable to any particular age group (such as the oldest). In contrast, for those infected abroad, a lower standardized mortality ratio 0.3 (95% CI: 0.04-0.8) was shown for the first month after diagnosis compared to what would be expected in the general population.

Conclusion: Infection with Campylobacter is associated with an increased short-term risk of death among those who were infected domestically. On the contrary, for those infected abroad a lower than expected risk of death was evident. We suggest that the explanation behind this is a "healthy traveler effect" among imported cases, and effects of a more frail than average population among domestic cases.