Malaria elimination surveillance — DTM&H MCQ

Correct answer: D — Case investigation and reactive case detection within 1 km radius

The correct answer is D, case investigation and reactive case detection within 1 km radius. In malaria elimination and prevention-of-reintroduction settings such as Sri Lanka, WHO's surveillance strategy treats every single case, especially one detected passively, as a potential focus of ongoing transmission that must be actively contained. This follows the WHO-endorsed 1-3-7 approach: notification within 1 day, case investigation and classification within 3 days, and a full response including reactive case detection (screening contacts and neighbours, typically within a 1 km radius of the index case) within 7 days. This targeted, proportionate response identifies any secondary or hidden cases early, determines whether the case is imported, introduced, or indigenous, and guides vector control decisions without wasting resources on a blanket intervention. Why the other options are wrong: C. Epidemic response with mass drug administration: mass drug administration is reserved for confirmed active foci with ongoing local transmission or outbreak clusters, not a single passively detected case, and is resource-intensive and not first-line in elimination settings. E. No action required for a single case: in elimination settings every case, however isolated, risks re-establishing transmission, so passive surveillance detection must always trigger investigation; ignoring it contradicts WHO elimination certification requirements. A. Immediate district-wide indoor residual spraying: spraying an entire district is disproportionate and untargeted; vector control response should follow focus investigation and be geographically limited to the confirmed or suspected transmission focus. B. Travel restriction from the affected area: WHO does not recommend travel restrictions for malaria control, as they are neither evidence-based nor practical, and do not address the underlying need to identify the transmission source and any linked cases. Key point: in elimination settings, WHO's 1-3-7 strategy mandates that every single case, however detected, prompts prompt case investigation and localised reactive case detection to prevent re-establishment of transmission.

Reference: WHO, Global Technical Strategy for Malaria 2016-2030 and WHO Malaria Surveillance, Monitoring and Evaluation: A Reference Manual (2018), section on the 1-3-7 approach and reactive case detection in elimination settings, https://www.who.int/publications/i/item/9789241549691