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 30 th 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; E p u b a h e a d o f p r i n t 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.

The peripartum period is both a highly vulnerable stage and a significant indicator of a population's health status. Interest is increasing in Human T-cell leukemia virus type-1 (HTLV-1) transmission due to its adverse health impacts. However, nationally representative data on HTLV-1 that are important for health planning are unavailable for this subpopulation.This study aimed to conduct a pooled estimate of HTLV-1 prevalence among pregnant women in Nigeria to quantify its clinical burden and public health implications. This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis 2020 statement. After a systematic review of the Nigerian literature, 12 studies (2821 pregnant or postnatal women) were included in the final evidence synthesis. The estimated HTLV-1 prevalence in Nigerian peripartum women following a positive screening test by enzyme-linked immunosorbent assay was 5.44% (95% confidence interval [CI], 3.16-9.20%). A subgroup analysis of the two major regions showed a slightly higher prevalence in the Western versus Southern region (5.55% [95% CI, 2.49-11.87%]; and 4.91% [95% CI, 2.11-11.02]; P = 0.84). However, a subgroup analysis by geopolitical zone revealed that Southwestern and Northwestern Nigeria had the highest prevalence (9.23% [95% CI, 4.35-18.55; I 2 , 93%] and 7.15% [95% CI, 1.54-27.54]; I 2 , 92%).Our decade-old subgroup analysis found inconsistencies in the HTLV-1 prevalence. Furthermore, our literature review revealed a prevalence of HTLV infection among patients with various clinical types of lymphomas/leukemias and myelopathy of 2-22%. These findings have important implications in defining the epidemiological patterns of HTLV-1 infection in Nigeria. They also suggest the presence of HTLV-endemic clusters near lowendemic areas, even within the same geopolitical zones.