Utilization of case definitions and laboratory reporting in the surveillance of notifiable communicable diseases in the United States.

In 1984, questionnaires were sent to the chief epidemiologist in all 50 states, Puerto Rico, and Washington, DC, with a 100 per cent response rate. There were substantial variations in case definitions of reportable diseases, criteria for counting as a case, and sources of surveillance. Laboratory reporting of any notifiable condition is mandated by 54 per cent of jurisdictions. These differences in ascertainment and case-counting practices constitute potential sources of error in national surveillance data on communicable diseases.