Epidemiological trends of Lassa fever in Nigeria from 2015-2021: A review

Abstract

Introduction: Lassa fever is a viral haemorrhagic fever with non-specific symptoms that has shown an upward trend in Nigeria and other West African countries, which is depicted by high incidence and case fatality in recent years. There are different reports on the yearly case burden of Lassa fever from the Federal Ministry of Health in Nigeria, through the regulatory body – Nigeria Centre for Disease Control (NCDC). Being the epicentre of the disease, Lassa fever has been exported from Nigeria to both neighbouring and distant countries.Methods: The aim of this review was to carry out a retrospective analysis from January 2015 to 26 September 2021 of the weekly and yearly outbreak of Lassa fever in Nigeria based on selected publications. The focus was on timely diagnosis, treatment option, public health interventions and progress of clinical trials for vaccine candidates, and to identify proactive measures that can be sustained to curb periodic outbreaks. The review was done using percentages, cross-tabulation and graphical charts. Results: The predominant age group infected was 21 to 40 years with a male to female ratio of 1:0.8. A total of 3311 laboratory-confirmed Lassa fever cases out of 20,588 suspected cases were identified from 29 states. Edo, Ondo, Taraba, Ebonyi, Bauchi, Plateau and Nasarawa had yearly Lassa fever incidence over the time frame considered. Contact tracing was done on over 33,804 individuals with about 90% completing follow-up. Case fatality rate within the period ranged from 9.3% to 29.2%. There is a sharp decline in the epidemiological trend of Lassa fever in the yearly seasonal peaks from weeks 1 to 13 with about 75% reduction in incidence between 2020 and 2021. Conclusion: The effective management of Lassa fever needs the implementation of preventive methods, prompt laboratory diagnosis, timely treatment, provision of personal protective equipment, cross-border surveillance, contact tracing, community awareness and vector control in order to minimise spread.

Re‐emergence of Lassa fever in Nigeria: A new challenge for public health authorities

“…Throughout the years, the predominantly affected age group was between 20 and 30 years. [14][15][16][17] In 2021, a surprising decline was witnessed in the number of cases, as 510 patients in 17 states were confirmed to have Lassa fever. With 102 mortalities, a case fatality rate (CFR) of 20% was also reported to be reduced at the end of the year.…”

“…In 2020, amidst the Coronavirus pandemic, the cases uncontrollably increased to 1189 laboratory‐confirmed cases with 244 deaths. Throughout the years, the predominantly affected age group was between 20 and 30 years 14–17 …”

Lassa fever in Nigeria: Social and Ecological Risk Factors Exacerbating Transmission and Sustainable Management Strategies

“…Achieving the sustainable development goals requires a healthy environment, which is also tied to sustainable governance models that will engage multiple intersectoral links [97]. This point was further emphasized by Grace, et al [98] wherein they suggest that effective management of Lassa fever should focus on the implementation of preventative methods, prompt diagnosis, and treatment, ensuring the availability of personal protective equipment, contact tracing, community awareness, and cross border monitoring and surveillance. In addition, the characterization of the epidemiological profiles of Lassa fever should be ongoing and made a priority even outside the West Africa subregion [99].…”

Current Trends of Lassa fever amidst COVID-19 Pandemic in Nigeria

“…Lassa fever is endemic in Nigeria and cases peak annually during the dry season (December -April) and decrease in May [5]. The incubation period for Lassa fever is between 1 -3 weeks, which can lead to infection spread from region to region [6]. The rodent host is the primary driver of the Lassa fever seasonal trends, with reproduction cycles of the multimammate rat increasing during the rainy season [7].…”