Late diagnosis of Lassa fever outbreak in endemic areas lead to high mortality, Kenema District, Sierra Leone, February - March 2019.

Introduction: the Kenema District Surveillance team in Sierra Leone received notifications of patients with suspected Lassa fever on February 20 and March 2, 2019. On that day, an investigation started to confirm the diagnosis and search for additional cases.

Methods: we used the Lassa fever surveillance case definition and collected demographic and exposure information from suspected cases through interviews and clinical records.