Shortening outbreak-response delays: A multi-source synthesis of six lessons from Sierra Leone’s 2025 clade IIb mpox response

Sierra Leone confirmed mpox on January 10, 2025, and declared an emergency three days later. National surveillance recorded 5,442 confirmed cases and 60 deaths (1.1%) through December 14. The last case received laboratory confirmation on October 25. The outbreak was declared over on December 15. We identified operational lessons for shortening future outbreak-response delays. We retrospectively synthesized the January–December response through document analysis, triangulation, and informal expert consensus. Sources included field experience, national surveillance and response reviews, an early 44-case analysis, a four-district qualitative study of 140 participants, and genomic reconstruction. Six lessons address illness onset to presentation, presentation to actionable diagnosis, and diagnosis to initiation of supported transmission-interruption measures. Early cases presented a median of five days after onset. The median onset-to-confirmation interval was eight days. A genomic model estimated approximately 10,400 infections (95% highest posterior density interval, 7,000–15,200), against 5,096 laboratory-confirmed cases in that analysis. District teams should protect confidential care seeking, sustain rash recognition and sampling, and track result communication. They should support feasible isolation, plan sustained staffing, and connect specimens to national and regional sequencing. Notifications declined before the enhanced response phase, and concurrent interventions prevent separate effect estimates. The declared outbreak end does not exclude undetected transmission. A proposed district package links these lessons to responsible officers, indicators, review triggers, and resources for prospective evaluation.