What are the three phases of outbreak investigation (field epidemiology)?

• A. Descriptive phase; Analytic phase; Intervention phase
• B. Phase I; Phase II; Phase III
• C. Data collection; Data analysis; Reporting
• D. Hypothesis generation; Experiments; Publication

Answer: (A)

Descriptive phase, Analytic phase, Intervention phase.

In outbreak field epidemiology, you start by describing the outbreak: who is affected, where and when it began, and the characteristics of cases. This involves collecting case counts, building line lists, and creating epidemic curves to see patterns in person, place, and time. This descriptive work helps generate initial hypotheses about possible sources or causes.

Next, you test those hypotheses with analytic methods. This phase uses study designs like cohort or case-control studies to compare exposures between those who became ill and those who did not. The goal is to identify associations and quantify risk, helping to pinpoint the source, vehicle, or risk factors driving the outbreak. This is where you move from description to causal insight.

Finally, you move to the intervention phase: implement control and prevention measures based on the analytic findings, communicate with the public and stakeholders, and monitor the impact of those interventions. This phase closes the loop by reducing transmission and evaluating whether the actions were effective.

Other groupings either describe general data processing steps or focus on research activities rather than the field-epidemiology response sequence, so they don’t align with how outbreak investigations are typically structured in practice.