The decision to investigate is influenced by…

• morbidity / mortality

• unusual presentation – rare disease, change in pattern, new disease

Control - prevent additional cases; prevention – prevent future outbreaks

Research opportunities – identify new risk factors; define natural history and spectrum of the disease; measure impact of control measures or clinical interventions; etc.

Program considerations – an outbreak may represent a failure or gap in public health program. Need to investigate to determine why.

Public / political / legal concern – health department needs to be “responsibly responsive”