Verify the diagnosis and confirm the outbreak: The first step in an investigation is to determine whether the reported number of cases is unusual. Baseline surveillance data is a useful resource for making this decision. Verifying the diagnosis through laboratory testing is also important, especially for new or uncommon pathogens.
Define a case and conduct case finding: Investigators should establish a case definition by characterizing cases by clinical signs and symptoms and epidemiologic information related to person, place, and time. Using the case definition, investigators can search for additional cases.
Tabulate and orient data: time, place, person: Information about possible cases should be organized in a line listing and summarized according to time, person, and place.
Take immediate control measures: If the source of the outbreak is apparent and still a potential threat to public health, appropriate control measures should be taken as quickly as possible. Examples of control measures are closing a restaurant, prohibiting swimming in a certain area, and enacting isolation and quarantine
Formulate and test hypothesis: At this point, investigators develop a hypothesis about the cause of the outbreak. Understanding the possible disease pathogen and mode of transmission is useful when creating hypotheses.
Plan and execute additional studies: Depending on available resources, investigators may test a hypothesis using an analytic study, such as a case-control study or retrospective cohort study.
Implement and evaluate control measures: Once the cause of the outbreak has been identified investigators should work to implement longer-term control measures to end the current outbreak and prevent future outbreaks. These control measures are more extensive than earlier control measures and should be evaluated to determine if they are effective. Examples of such measures are: recommending different food safety procedures in a restaurant, implementing better disinfection protocols at a local swimming pool
Communicate findings: Throughout the investigation, investigators should communicate findings within their agency, to other organizations, and to the general public. Outbreaks provide a unique opportunity to educate the general public about health promotion and disease prevention.
