Lassa fever in Sierra Leone: Increasing number of confirmed cases reported
In the past week, the Sierra Leone Ministry of Health (MoH) reported 38 new Lassa fever cases (6 confirmed, 32 suspected), including four deaths from two counties.
This brings the total to 39 cases (7 confirmed, 32 suspected) and 5 deaths (CFR 71%) from three of 16 counties in 2025.
The MoH updated the national Lassa fever surveillance protocol to enhance early detection of cases and response.
Since the beginning of the year, a total of 2,383 cases (423 confirmed) and 86 deaths (CFR 20%) from four African Union Member States, with Nigeria accounting for the vast majority of cases and deaths.
Lassa Fever is an acute viral illness and a viral hemorrhagic fever (VHF). The causative agent is a single-stranded ribonucleic acid (RNA) virus in the family arenaviridae, the Lassa virus. This zoonotic disease is associated with high morbidity and mortality, transmitted by the multi-mammate rat (mastomys natalensis), one of the most common rats in equatorial Africa.
The virus spreads through:
âą Direct contact with urine, feces, saliva, or blood of infected rats.
âą Contact with objects, household items, and surfaces contaminated with the urine, feces, saliva, or blood of infected rats.
âą Consuming food or water contaminated with the urine, feces, saliva, or blood of infected rats.
âą Person-to-person transmission can also occur through direct contact with blood, urine, feces, vomitus, and other body fluids of an infected person.
Lassa fever initially presents like other common illnesses accompanied by a fever, such as malaria. Other symptoms include headache, general body weakness, cough, nausea, vomiting, diarrhea, muscle pains, chest pain, sore throat, and, in severe cases, bleeding from ears, eyes, nose, mouth, and other body openings. The time between infection and the appearance of symptoms of the disease is 3 to 21 days. Early diagnosis and treatment of the diseases greatly increase the chances of patient survival.
Itâs not just COVID-19: Outbreaks of Lassa fever, plague and monkeypox
People most at risk for Lassa fever are:
âą People of all age groups who come in contact with the urine, feces, saliva, or blood of infected rats.
âą People living in rat-infested environments.
âą People who consume potentially contaminated foodstuff, especially those left open overnight or dried outside in the open.
âą People who handle or process rodents for consumption.
âą People who do not perform hand hygiene at appropriate times.
âą Caretakers of infected persons with poor infection prevention and control measures.
The disease was first discovered in a town called Lassa in Borno State, Nigeria in 1969.
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