Low Zika virus seroprevalence among pregnant women in North Central Nigeria, 2016

Background: Zika virus (ZIKV) has been known for decades in Africa but contemporary data is lacking at large. Objectives: To describe the seroepidemiology of ZIKV in North Central Nigeria. Study design: We performed a cross-sectional study at six health care facilities in North Central Nigeria from January to December 2016. Detection of ZIKV antibodies was done using an anti-ZIKV recombinant nonstructural protein 1 (NS1)-based ELISA. A colorimetric assay to detect ZIKV neutralizing antibodies was used on ELISA reactive and randomly selected ELISA non-reactive samples. ZIKV real-time RT-PCR was done on a subset of samples. Results: A total of 468 individual samples were included with almost 60% from pregnant women. Using NS1-based ELISA, an anti-ZIKV positive rate of 6% for IgM and 4% for IgG was found. Pregnant women showed anti-ZIKV positive rates of 4% for IgM and 3% for IgG. None of the ZIKV antibody positive samples tested ZIKV RTPCR positive. An association with male sex was found for anti-ZIKV IgG ELISA positivity (prevalence ratio 3.49; 95% confidence interval: 1.48-8.25; p=.004). No association with pregnancy, yellow fever vaccination or malaria was found for anti-ZIKV IgM or IgG positivity. ZIKV neutralizing antibodies were detected in 17/ 18 (94%) anti-ZIKV NS1 positive/borderline samples and in one sample without detectable ZIKV NS1 antibodies. Partial ZIKV E gene sequence was retrieved in one sample without ZIKV antibodies, which clustered within the West African ZIKV lineage. Conclusions: Our results show a largely ZIKV immunologically naive population and reinforce the importance of ZIKV surveillance in Africa.