LASSA FEVER OUTBREAK INVESTIGATION IN TONKOLILI DISTRICT, MARCH 2022

Abstract

Background: Lassa fever is an endemic zoonotic disease in West African countries, including Sierra Leone. On March 3, 2022, Tonkolili District Surveillance Unit received notification of suspected Lassa fever cases from a hospital. The Sierra Leone Field Epidemiology Training Program (SLFETP) trainees and mentors responded within 24 hours to confirm the diagnosis, identify sources, and institute control measures.

Methods: We interviewed case patients and families using a case investigation form; reviewed patients’ records; collected blood specimens and sent them to the Reference Laboratory.  Environmental assessment, rodent trapping, and an active case search were conducted, and 29 contacts were line-listed and monitored for 21 days.

Result: Two suspected cases tested positive for Lassa fever. On February 25, 2022, a 5-year-old male (Case 1) developed fever, abdominal pain, and diarrhea, he was admitted to the hospital on March 1, 2022, and treated for malaria. He died on March 3, 2022, Lassa fever was suspected and later confirmed by Polymerase Chain Reaction (PCR) testing. An 8-year-old girl (Case 2) who developed skin rashes and fever on February 25, 2022, was treated with traditional herbs at home. She was admitted to the hospital on March 1, 2022, as her symptoms persisted and was treated for malaria. Two days later, Lassa fever was suspected, and the diagnosis was confirmed four days after admission. She died on the same day of laboratory confirmation. Both patients lived in the same household with no travel history. Poor environmental sanitation was observed around the patients’ households. No rodents were found, and no additional cases or symptomatic contacts were discovered.

Conclusion: Two Lassa fever cases were confirmed in Tonkolili District. Late detection by healthcare workers likely contributed to the patient's deaths. We sensitized healthcare workers on the Lassa fever case definition and recommended community education on early healthcare seeking.

Keywords: Lassa fever, Disease outbreak, Zoonoses, Polymerase chain reaction, Sierra Leone.