Reports of outbreaks of food- and waterborne disease in Canada and the United States were searched for data on the number of cases of illness initially reported to health and food protection agencies. These were compared to the number of cases identified by thorough epidemiological investigations or to the number estimated. For a total of 51 outbreaks of bacterial, viral, and parasitic disease, the median ratio of the estimated cases to initially reported cases was 25:1. Based on this ratio and the systems of data transmission from the first level of reporting to national reporting agencies, the estimates of annual food and waterborne disease cases for 1974 to 1975 were from 150,000 to 300,000 in Canada and 1,400,000 to 3,400,000 in the United States. For a total of 26 outbreaks of salmonellosis, the median ratio of estimated cases to initial buman isolations of Salmonella was 29.5. Based on this ratio and reported isolations of Salmonella from 1969 to 1978, the estimates of all cases of human salmonellosis were 150,000 in Canada and 740,000 in the United States, annually.
1Health Protection Branch.
2Center for Disease Control.