Systematic review and meta-analysis of the epidemiology of Lassa virus in humans, rodents and other mammals in sub-Saharan Africa

Accurate data on the Lassa virus (LASV) human case fatality rate (CFR) and the prevalence of LASV in humans, rodents and other mammals are needed for better planning of actions that will ultimately reduce the burden of LASV infection in sub-Saharan Africa. In this systematic review with meta-analysis, we searched PubMed, Scopus, Africa Journal Online, and African Index Medicus from 1969 to 2020 to obtain studies that reported enough data to calculate LASV infection CFR or prevalence. Study selection, data extraction, and risk of bias assessment were conducted independently. We extracted all measures of current, recent, and past infections with LASV. Prevalence and CFR estimates were pooled using a random-effect meta-analysis. Factors associated with CFR, prevalence, and sources of between-study heterogeneity were determined using subgroup and metaregression analyses. This review was registered with PROSPERO, CRD42020166465. We initially identified 1,399 records and finally retained 109 reports that contributed to 291 prevalence records from 25 countries. The overall CFR was 29.7% (22.3–37.5) in humans. Pooled prevalence of LASV infection was 8.7% (95% confidence interval: 6.8–10.8) in humans, 3.2% (1.9–4.6) in rodents, and 0.7% (0.0–2.3) in other mammals. Subgroup and metaregression analyses revealed a substantial statistical heterogeneity explained by higher prevalence in tissue organs, in case-control, in hospital outbreak, and surveys, in retrospective studies, in urban and hospital setting, in hospitalized patients, and in West African countries. This study suggests that LASV infections is an important cause of death in humans and that LASV are common in humans, rodents and other mammals in sub-Saharan Africa. These estimates highlight disparities between sub-regions, and population risk profiles. Western Africa, and specific key populations were identified as having higher LASV CFR and prevalence, hence, deserving more attention for cost-effective preventive interventions.Author summary: Lassa virus (LASV) infection constitutes a major public health threat as it has a direct impact on the mortality of febrile patients, healthcare workers, pregnant women, visitors of endemic countries with a consequential negative impact on national and individual economies. It is necessary to have accurate epidemiological data on LASV infection, in order to prioritize the policies, funding for public health interventions, and health-care planning, especially in sub-Saharan Africa (SSA). Data concerning virus occurrence in rodents and other mammal species can also assist in guiding control of Lassa fever from an ecological perspective. This could include preventive measures such as the protection of food fields by anti-rodent barriers, the protection of rodent predatory fauna, the sanitation of home and particularly the food storage place and the blocking of rodent access to home and food stored. Our systematic review and meta-analysis of LASV infection in SSA has contemporarily and comprehensively summarized the prevalence of current, recent, and past infection both in humans, rodents and other mammals. Broadly, the study showed relatively high CFR estimates in humans. Additionally, Western Africa presented the highest burden of LASV infections compared to other regions. This study emphasized various populations of SSA with relatively high burden of LASV infection. We have identified specific populations at high risk of LASV infection, who may urgently benefit from routine screening, detection and management programmes. Beyond, preventive strategies should be promoted, by educating and raising people’s awareness about LASV infection, and strengthening practitioners’ capacities towards adequate diagnosis and proper management of this infection in SSA.