Epidemiology of yellow fever virus in humans, arthropods, and non-human primates in sub-Saharan Africa: A systematic review and meta-analysis

Yellow fever (YF) has re-emerged in the last two decades causing several outbreaks in endemic countries and spreading to new receptive regions. This changing epidemiology of YF creates new challenges for global public health efforts. Yellow fever is caused by the yellow fever virus (YFV) that circulates between humans, the mosquito vector, and non-human primates (NHP). In this systematic review and meta-analysis, we review and analyse data on the case fatality rate (CFR) and prevalence of YFV in humans, and on the prevalence of YFV in arthropods, and NHP in sub-Saharan Africa (SSA). We performed a comprehensive literature search in PubMed, Web of Science, African Journal Online, and African Index Medicus databases. We included studies reporting data on the CFR and/or prevalence of YFV. Extracted data was verified and analysed using the random effect meta-analysis. We conducted subgroup, sensitivity analysis, and publication bias analyses using the random effect meta-analysis while I-2 statistic was employed to determine heterogeneity. This review was registered with PROSPERO under the identification CRD42021242444. The final meta-analysis included 55 studies. The overall case fatality rate due to YFV was 31.1% (18.3-45.4) in humans and pooled prevalence of YFV infection was 9.4% (6.9-12.2) in humans. Only five studies in West and East Africa detected the YFV in mosquito species of the genus Aedes and in Anopheles funestus. In NHP, YFV antibodies were found only in members of the Cercopithecidae family. Our analysis provides evidence on the ongoing circulation of the YFV in humans, Aedes mosquitoes and NHP in SSA. These observations highlight the ongoing transmission of the YFV and its potential to cause large outbreaks in SSA. As such, strategies such as those proposed by the WHO's Eliminate Yellow Fever Epidemics (EYE) initiative are urgently needed to control and prevent yellow fever outbreaks in SSA. Author summary Yellow fever, one of the most feared lethal zoonotic disease is re-emerging as a public health threat to tropical and sub-tropical countries of South America and Africa. Despite the existence of an effective yellow fever vaccine that is administered through mass vaccination campaigns and in routine immunization programs. against this disease, the mortality remains very high during the outbreak of yellow fever in several sub-Saharan African (SSA) countries. It is necessary to have accurate epidemiological data on YFV infection, in order to prioritize the policies, funding for public health interventions, and health-care planning. Our study is the first systematic review and meta-analysis with data provided on the case fatality rate (CFR) and prevalence of YFV in humans, and prevalence of YFV in arthropods, non-human primates (NHP), and other animal species in SSA. Broadly, the study shows that the CFR and prevalence of YFV in humans were relatively high and low respectively. Furthermore, mosquitoes of the genus Aedes and Anopheles funestus were the main vectors of YFV. Finally, only NHP of the Cercopithecidae family were the reservoirs of the YFV in SSA. These data provide evidence on the ongoing circulation of the YFV in SSA and the possibility of the large outbreaks YFV in SSA. Author suggests that preventive strategies should be promoted by educating and raising people's awareness about YFV infection and strengthening practitioners 'capacities towards adequate diagnosis and proper management of this infection in SSA.