Community-based malaria surveillance in Cambodia using a mobile reporting app for village malaria workers: An implementation case study.

To support malaria elimination, Cambodia implemented a locally developed, nationally integrated, community-based mobile digital surveillance system enabling real-time, case-based detection, reporting and response. This implementation case study describes the development, national deployment and operational performance of an Android-based mobile app used by Village Malaria Workers (VMWs) and Mobile Malaria Workers (MMWs) integrated within the national Malaria Information System (MIS). Developed collaboratively with VMWs, the system enables real-time, geolocated case reporting with offline functionality, built-in validation checks, centralized device management and automated analytics. Evaluation employed three data sources: routine surveillance data (2018-2024), a contextual survey of VMW/MMWs in three high-risk provinces (2024), and a national technical usability survey (2025). Outcomes included reporting timeliness, completeness, surveillance performance indicators aligned with the national malaria elimination framework and user experience. Following national implementation in 2017- 2018, data completeness and timeliness improved. Between 2018 and 2024 reporting coverage increased from 19% to 99% and data completeness has remained ≥99% since 2019. Case notification within 24 hours increased from 2% to 99% and foci investigation within 7 days from 0% to 98%. Malaria testing rates expanded from 135,664 to 715,277 per year. Intensified surveillance was concurrent with a decline in active malaria foci from 129 in 2020 to 0 in 2024. A contextual evaluation including 88 VMW/MMWs showed strong support for surveillance activities, including reporting and data analysis at the community level. The technical evaluation survey found that 94% (904/966) of VMWs were very satisfied/satisfied with the app, with technical problems experienced never/rarely by 82% (795/966). Key operational challenges included intermittent internet connectivity, limited electricity supply, and transport constraints, although offline functionality and data synchronization prevented data loss. Cambodia's experience demonstrates the feasibility and sustainability of large-scale digital surveillance in resource-constrained settings and highlights the importance of integration, training and sustainability through local ownership.