What is the final step in the seven-step outbreak investigation?

• A. Detect a possible outbreak
• B. Find cases in an outbreak
• C. Control outbreak through recalls
• D. Decide when the outbreak is over

Answer: (D)

Closing the investigation by deciding when the outbreak is over is the final step. After implementing control measures and confirming that transmission has ceased, public health teams monitor for new cases during a defined risk period (typically at least one incubation period for the disease). If no new cases appear, the outbreak is declared over, and a final report is prepared to document what happened, what was found, what controls were used, and the lessons learned. The earlier actions—detecting the outbreak, identifying cases, and carrying out control measures like recalls—occur in the earlier phases of the investigation, whereas the end of the outbreak marks the formal closure of the investigation.