Epidemiology, fatality rate, and geographic distribution of Lassa fever in Anambra state, Nigeria

Lassa fever remains a significant public health challenge in West Africa, with implications for regional health security. Despite its high morbidity and mortality rates, limited epidemiological studies have systematically examined the distribution, mortality burden, and geographic spread of the disease in this region. This study aims to provide an epidemiological analysis of Lassa fever cases in Anambra State, south-east, Nigeria, from 2018 to 2024. Specifically, this study examines the gender distribution, mortality rates, and local government area (LGA)-specific patterns of Lassa fever cases. A retrospective cross-sectional study of surveillance data from the Surveillance Outbreak Response Management and Analysis System (SORMAS) was conducted for confirmed, suspected, and probable Lassa fever cases from 2018 to epidemiological week 41 of 2024. The outcome measures included case distribution, mortality metrics, and geographic trends, highlighting Lassa fever’s prevalence, fatality rates, and high-burden areas. Descriptive statistics were used to calculate frequency distributions and detect trends in Lassa fever cases. Ethical approval for the study was obtained from the Anambra State Ministry of Health Research Ethics Committee. Following the accepted case definition of Lassa Fever, the study analysed 213 patients’ records with 9.9% confirmed cases, 23.9% suspected cases, and 64.8% non-cases despite presenting symptoms. Of the 21 confirmed cases, there was a slight male predominance (57% male and 43% female). Mortality analysis revealed that 38% of confirmed cases resulted in death, highlighting the severity of the disease and challenges in treatment accessibility. The highest prevalence was recorded in Anambra East LGA, followed by Ayamelum LGA. The majority of confirmed cases were among individuals aged 20–49 years. Trends indicate a fluctuating incidence over the years, with a peak in 2022. This study provides an exploratory analysis of Lassa fever epidemiology in Anambra State, underlining variations in case distribution, mortality, and geographic spread. However, the findings are limited by the retrospective nature of the study, potential underreporting, and the relatively small number of confirmed cases. The fluctuating incidence and concentration of cases in specific LGAs accentuate the need for enhanced surveillance and improved diagnostic capacity. Future research should employ community-based study designs and real-time surveillance systems to capture a more comprehensive picture of disease transmission dynamics and risk factors.