Background
In Liberia, Lassa fever (LF) cases have been recorded in previously disease-free areas, with a 56% fatality rate since December 2020. In March 2021, District # 3A &B reported a suspected Lassa fever outbreak at the Liberia Agriculture Company hospital. We investigated to confirm the outbreak, describe the magnitude, implement preventive and control measures.

Methods
We conducted descriptive cross-sectional study. A case was any person in Grand Bassa County with fever (>38 oC) and/or: malaise, sore throat, cough, nausea, vomiting, diarrhoea, myalgia, bleeding and absence of a response after 48 hours of anti-malarial treatment and /or broad spectrum antibiotic from the 27th February to 14th July 2021. We interviewed cases, reviewed outpatient registers, clinical records for demographics, clinical symptoms, and outcomes. Blood specimens were tested by real-time polymerase chain (rt-PCR). Active case search and contacts tracing was conducted. We assessed health education in affected communities and did environmental assessments. We summarized data into frequencies and proportions.

Results
Of the four cases confirmed, 50% were female, median age; 44 years (range:24-55). Attack rate was 8 per 100,000 and case fatality rate: 25%. Major signs & symptoms included; myalgia100 % (4/4), swollen neck100 %(4/4), sore throat 75% (3/4), nausea 75% (3/4). A total of 39 contacts were identified and quarantined. About 25.6% (10/39) were classified as high-risk contacts, most were females (69%) and health workers (59%). The affected community had overgrown weeds close to residential areas; consumption of rodents for food and garbage disposal in open areas encouraged rodent infestation. LF messages were aired to educate the public.

Conclusion
LF outbreak was confirmed in district # 3A and B. The findings suggested the outbreak was due to rodent ingestion, and poor sanitation. Timely risk communication, rodent control, and sanitation education helped control the outbreak. WASH-IPC interventions in health facilities should be improved to protect staff.