- Outbreak investigations are usually retrospective, often relying upon recall of affected persons to identify causal linkages.
- Because they begin without clear hypotheses, outbreak investigations require descriptive studies to generate hypotheses before analytic studies can be conducted.
- Since outbreak investigations are driven by an immediate health concern in the community, the need for responsiveness to community needs and effective risk communication is heightened.
- Outbreak investigations require public health officials to weigh the evidence, often in the absence of a clear etiologic connection, and determine when the data are sufficient to take controversial and sometimes unwelcome actions.
- Outbreak investigations often attain national or international prominence (eg, toxic shock syndrome, E. coli food contamination)