Campylobacteriosis in the Nordic countries from 2000 to 2015: Trends in time and space

Aims: This study aimed to describe the demographic and geographic patterns of campylobacteriosis in Denmark, Finland, Norway and Sweden during 2000–2015. Methods: All Campylobacter infections notified to national authorities in the four countries during the study period were included. Background data for each notification consisted of patient age, sex, geographical location, presumed origin of infection and date of sample taken or date of sample received in the laboratory. These data were analysed in order to investigate annual trends, age group and sex patterns, as well as variations in the geographical and seasonal distribution of infections. Results: During the study period, a total of 164,001 Campylobacter infections, excluding travel-related cases, were registered, representing a mean annual incidence of 42.3 cases/100,000 population (ranging from 28.5 in Norway to 60.4 in Denmark). The incidence increased significantly from 2004 onwards in all countries, apart from Denmark. Males had higher infection rates in general. The highest incidences were observed in 0–4 year olds and those aged 20–29 years, apart from in Finland where there was no peak of infections in children aged 0–4 years. Seasonality of disease was distinct in all four countries, showing peaks of infection between July and August. In Sweden and Norway, incidences of campylobacteriosis were significantly higher in municipalities with high degrees of coastline or inland water. Conclusions: Campylobacter in the Nordic countries mostly follows known patterns with respect to demography and seasonality. Our study demonstrates new insights concerning geographical patterns of disease, highlighting possible future vulnerable population groups and locations.