Trend and Descriptive Epidemiology of Lassa fever in Ebonyi State, 2018 - 2022

Abstract

Background Lassa fever’s emergence in Nigeria has been a public health concern over the years. Ebonyi state is located in the South-Eastern zone of Nigeria where a high burden of Lassa fever has been reported. Assessment of trend and risk factors for Lassa fever are yet to be fully explored in the state. We investigated the trend and descriptive epidemiology of Lassa Fever in Ebonyi state, South-East, Nigeria. Method This study was analysis of data extracted from Ebonyi State Integrated Disease Surveillance and Response (IDSR) system over a five-year period (2018-2022). A total of 1578 reported Lassa fever cases was captured in the IDSR out of which 300 were laboratory-confirmed. The trend and seasonality of Lassa fever were assessed using an additive time series model to ascertain the quarter of the year when the disease is expected to be at its peak. Lassa fever cases were predicted using the identified fitted model among the linear, quadratic, cubic and exponential models (α0.05). Results The mean age of the individuals with the reported cases of Lassa fever was 29.4 ± 17.8 years. Lassa fever showed a seasonal trend across the years. The quadratic model provided the best fit for predicting Lassa fever cumulative cases (R2 = 98.4%, P-value <0.05). Projected cases of Lassa fever for the year 2023 were 123 in the 1st quarter, 23 in the 2nd quarter, 42 in the 3rd quarter, and 17 in the 4th quarter. The seasonality index was +70.76, -28.42, -9.09, and -33.2 in the 1st, 2nd, 3rd, and 4th quarters respectively. The reported cases of Lassa fever followed a declining trend (slope= -0.1363). Farmers were 70% less likely to die from Lassa fever compared to those not working (aOR:0.3, CI: 0.17-0.83). Conclusion: Although the reported Lassa fever cases followed a declining trend in Ebonyi state, there was a seasonality in the trend over the study period. Adequate preparedness to mitigate the spread of the disease during the peak period of the disease is recommended.