Epidemiology of infections with enteric salmonellae in Switzerland with particular consideration of travelling activities.

QUESTIONS UNDER STUDY To describe the current epidemiological situation of enteric salmonellosis in Switzerland and its development in the last two decades, particularly by determining the ratio between domestic and travel-associated cases. METHODS Between 1 February 2011 and 31 January 2012, 14 medical laboratories continuously reported their isolations of enteric salmonellae to the Federal Office of Public Health (FOPH). Data on the travel history of salmonellosis patients was actively acquired from their treating physicians. These data were compared with the results of a case-control study on sporadic salmonellosis that was performed in 1993. RESULTS It could be shown that, concomitantly with the pronounced decline in incidence of reported laboratory notifications of enteric salmonellae since the early 1990s, the travel-associated portion of isolates belonging to the most frequently isolated serovar Enteritidis has increased significantly (more than doubled). The three serovars that followed S. Enteritidis in frequency of isolation (Typhimurium, Bardo, monophasic 4,12:i:-) are predominantly of domestic origin. CONCLUSIONS The significant increase in the percentage of travel-related S. Enteritidis infection, demonstrated by the comparison between the data from 2012 and 1993, might be a consequence of the reduction in domestic infections during this period. The fact that infections due to this serovar are now significantly more often travel-related than domestic clearly illustrates the success of the preventive measures taken. These consist of legal measures that were necessary to reduce the transmission of the pathogen in raw eggs, and sanitation measures taken by the producers that aimed to contain the chicken meat reservoir.