Evolution of Zika prevalence in a dengue hyperendemic municipality in Southern Mexico after the outbreak of 2015 to 2017

Objective. Estimate the Zika prevalence in a dengueendemic municipality in Mexico, after the outbreak of 2015 to 2017. Materials and methods. Three serosurveys were conducted in Tapachula, Chiapas, in September 2018, March 2019 and November 2019. A commercial ZIKV and DENV anti-NS1 IgG ELISA were used to estimate each prevalence, their performance and adjustment of the cut-off value were compared with an in-house DENVs and ZIKV anti-EDIII IgG ELISA and the microneutralization test. Results. The anti-NS1 ZIKV titers decreased over time, causing that Zika prevalence decreased from 78.02 to 45.22%, while anti-NS1 DENV titers increased, and the prevalence remained above 95% over a two-year period. Conclusion. Optimal Zikaprevalence estimates can be obtained in a two-years period after outbreaks in dengue-endemic areas. The extension of the Zika outbreak is significantly higher than previously reported in Tapachula, highlighting the underreport of cases based on the routine flavivirus surveillance system in Mexico.