Stool submission data to help inform population-level incidence rates of enteric disease in a Canadian community

Laboratory-based surveillance data is essential for monitoring trends in the incidence of enteric disease. Current Canadian human enteric surveillance systems report only confirmed cases of human enteric disease and are often unable to capture the number of negative test results. Data from 9116 hospital stool specimens from the Waterloo Region in Canada, with a mixed urban and rural population of about 500 000 were analysed to investigate the use of stool submission data and its role in reporting bias when determining the incidence of enteric disease. The proportion of stool specimens positive for Campylobacter spp. was highest in the 15-29 years age group, and in the 5-14 years age group for Salmonella spp. and E. coli O157:H7. By contrast, the age-specific incidence rates were highest for all three pathogens in the 0-4 years age group which also had the highest stool submission rate. This suggests that variations in age-specific stool submission rates are influencing current interpretation of surveillance data.