Table 1.

Major types of surveillance systems in public health.

Purpose	Outbreak response	Health program planning
System design:	Case finding: identify infected individuals	Sentinel surveillance: track prevalence over time
Resulting action:	Isolate and treat	Adjust policies and programs
Key characteristic:	Specific: pinpoint individuals for rapid follow-up	Comparable: standardized methods allowing comparison over time
Cannot be used to:	Estimate prevalence; track trends over time	Respond at individual level