Descriptive epidemiology of infections due to thermotolerant Campylobacter spp. in Norway, 1979-1988.

This report reviews the first ten years of Campylobacter surveillance in Norway. During 1979-1988, a total of 3,545 isolates of thermotolerant Campylobacter spp. were reported. The isolation rate increased from 1.8 per 100,000 persons per year in 1979 to 13.1 in 1988. The highest isolation rate for both sexes occurred during the first five years of life (31.0 per 100,000). A smaller second peak was detected in the age group 15-24 years (11.1 per 100,000). The male-to-female ratio was 1.52:1 for infants less than five years of age, compared with a ratio of 1.35:1 for all ages combined. Thirty-eight percent of the infections had most probably been acquired abroad. The isolation rate in urban areas (12.4 per 100,000) was over twice that observed in rural agricultural municipalities (5.5 per 100,000). However, this difference was largely due to a higher proportion of imported cases in urban areas, only small variations in isolation rate were observed when imported cases were excluded. The seasonal distribution of Campylobacter isolates showed a peak during the warm months of the year. Travel activity during summer holidays did not account for this trend, since the summer peak became even more pronounced when imported cases were excluded. A north-south gradient in the seasonality was observed; when domestic cases were considered, the summer peak became more accentuated with increasing latitude reaching a maximum in subarctic areas. This might be explained by corresponding variations in occurrence of campylobacters in surface water sources.