Seroprevalence of Zika Virus immunoglobulin G among pregnant women in Thailand during 1997-2014

Abstract

Zika virus (ZIKV) infection had emerged in Western Pacific in 2007 and rapidly spread to several areas in the world. ZIKV was declared a public health emergency of international concern in 2016. However, epidemiological data on the situation of ZIKV in Thailand is still limited. This study aimed to 1) assess ZIKV IgG seroprevalence among young adults in Thailand during the period 1997-2017, 2) assess whether ZIKV seroprevalence depends on HIV status and, 3) determine the factors associated with ZIKV IgG seropositivity. I performed a retrospective laboratory study using plasma samples and data collected during several large clinical studies conducted between 1997 and 2017 in Thailand that included HIV-infected, HIV-uninfected, and HBV-infected pregnant women as well as general population. ZIKV IgG was assessed on stored plasma/serum samples using the Anti-Zika Virus IgG ELISA (EUROIMMUN, Germany). The proportions of ZIKV IgG seropositivity between each period and between the HIV- infected and -uninfected groups were compared using the Chi-Square test. Univariable and multivariable analysis were performed to identify factors associated with ZIKV IgG positivity. ZIKV IgG seroprevalence in the country seems to be stable ranging from 24.3% to 27.4% and the overall prevalence was 23.1% in general population and 25.2% in pregnant women. ZIKV IgG seroprevalence was similar in HIV-infected and HIV- uninfected pregnant women (22.8% vs 25.8%, p-value = 0.335). Factors independently associated with a high rate of ZIKV IgG positivity included being aged 23-25 years and having HIV RNA load below 3.88 log10 copies/mL, while being born in Northern region of Thailand independently associated with a low rate of ZIKV IgG positivity. Our study suggests that a large proportion of young adult in Thailand probably remains susceptible to ZIKV infection. Continued surveillance of the ZIKV spread is needed to monitor the incidence of ZIKV infection in Thailand in young population, its possible impact on birth outcomes, and plan measures to prevent the outbreak in the future.