Morbidity and Mortality Patterns of Lassa Fever at a Tertiary Treatment Centre in Southern Nigeria: A Five-Year Retrospective Review

Background: Lassa fever remains a major public health challenge in West Africa, particularly in Nigeria where recurrent outbreaks continue to place pressure on health systems. Facility-based analyses are important for understanding morbidity and mortality trends in endemic regions. Objective: To assess morbidity and mortality trends of Lassa fever among patients managed at Irrua Specialist Teaching Hospital over a five-year period. Methods: A retrospective hospital-based cross-sectional study was conducted at Irrua Specialist Teaching Hospital, Edo State, Nigeria. Case records of all patients with confirmed Lassa fever managed between January 2018 and August 2022 were reviewed. Data were extracted using a structured checklist and analysed using SPSS version 23. Descriptive statistics were used to summarise socio-demographic, clinical and outcome variables. Results: A total of 191 Lassa fever case records met the eligibility criteria. The estimated mean age was 26.0 ± 18.8 years, with most patients younger than 30 years. There was a slight male predominance (52.4%). Admissions peaked in 2018 (47.1%) and declined thereafter. Most patients presented within five days of symptom onset (46.1%), although 17.8% presented after more than 11 days. The most common symptoms were fever (91.1%), vomiting (50.3%), headache (46.6%), and anorexia (46.1%), while haemorrhagic manifestations were uncommon (4.7%). The overall case fatality rate was 13.6%. Most hospital admissions lasted 6–15 days. Conclusion: Lassa fever remains an important cause of hospital admission and mortality in Edo State. Although mortality in this cohort was within previously reported hospital-based ranges, delayed presentation and non-specific clinical features remain challenges for early diagnosis. Strengthening surveillance systems, improving early detection, and enhancing infection prevention practices are essential to reducing Lassa fever morbidity and mortality in endemic settings.