Distribution Pattern and Prevalence of West Nile Virus Infection in Nigeria; 1950 to 2020 Systematic Review.

Objectives West Nile virus (WNV) is a re-emerging mosquito-borne and zoonotic viral infection which is largely underestimated in Nigeria. This study sought to determine the pooled prevalence pattern and risk factors of WNV infection among humans and animals in Nigeria. Methods A systematic review of eligible articles was conducted from "PubMed", "Scopus", "Google Scholar" and "Web of Science", from 1 st January 1950 to 30th August 2020. Peer-reviewed articles describing WNV infection of humans and animals in cross-sectional studies were systematically reviewed and analyzed. Cochrane Q was used to determine the heterogeneity of studies reports. Results About 61.5% human studies had low risk of bias. Howewer, all had high heterogeneity. Southwestern Nigeria had the highest pooled prevalence of anti-WNV IgM, 7.8% in humans. The pooled WNV IgM and IgG seroprevalence were 7.1% (95% CI: 5.9 - 8.3) and 76.5% (95% CI: 74.0 -78.8), respectively. The WNV RNA prevalence was 1.9% (95% CI: 1.4 - 2.9), while 14.3% (95% CI: 12.9-15.8) had WNV neutralizing antibodies. In animals, the pooled WNV IgM and IgG seroprevalence were 90.3% (95% CI: 84.3 - 94.6) and 3.5% (95% CI: 1.9 -5.8), respectively while 20.0% (95% CI: 12.9-21.4) had WNV neutralizing antibodies. Age (OR=3.73, 95% CI: 1.87-7.45; p=0.0002) and level of education [no formal education (OR=4.31, CI: 1.08-17.2; p=0.0386), primary (OR=7.29, 95% CI: 1.80-29.6; p=0.0054)], were significant risk factors of WNV IgM seropositivity in humans. Conclusion Findings from this study highlighted the endemicity of WNV infection in animals and humans in Nigeria and underscored the need for "One health" prevention and control approach against WNV infection.