West Nile Virus in Africa: Current Epidemiological Situation and Knowledge Gaps

Purpose: West Nile virus (WNV) is an arthropod-borne zoonotic pathogen which represents a continuous source of concern for public health worldwide due to its expansion and invasion into new regions. Its distribution and circulation intensity in African countries is only partially known. The aim of the present study is to provide an updated overview on the current knowledge of WNV epidemiology in Africa, providing available data on incidence in humans and animals, the circulating lineages and clades, other than an updated list of the principal arthropod vectors identified and the availability of vector competence studies. Methods & Materials: We searched pertinent articles to be included in the Scoping Review according to PRISMA and QUO- RUM criteria. We searched PubMed and Google Scholar electronic databases on January 21, 2020, using selected keywords. From the references of each article, we explored further references as appropriate. Additional references have been later identified and added accordingly to expert opinion. Results: This review, based on the analysis of 150 scientific papers published between 1940 and 2020, highlights: (i) the co-circulation of WNV-lineages 1,2, and 8 in the African continent; (ii) the circulation of Koutango virus in Senegal, Gabon, Somalia, and Niger (iii) the presence of diverse WNV competent vectors in Africa, mainly belonging to the Culex genus; (iv) the lack of vector competence studies for several other mosquito species found naturally infected with WNV in Africa; (v) evidence of the circulation of WNV among humans, animals and vectors in at least 28 Countries; and (vi) the lack of knowledge on the epidemiological situation of WNV for 19 Countries. Conclusion: This study provides the state of art on WNV investigation carried out in Africa, highlighting several knowledge gaps regarding i) the partial knowledge on the current WNV distribution and genetic diversity, ii) its ecology and transmission chains including the role of different arthropods and vertebrate species as competent reservoirs, and iii) the real disease burden for humans and animals, therefore highlighting the needs for further research and surveillance studies to be addressed with high priority in this Continent.