Survey on neutralizing antibodies against Zika virus eighteen months post-outbreak in two southern Thailand communities

Abstract

Background In 2016 and 2017, Zika virus (ZIKV) infection outbreaks occurred in two communities in southern Thailand. This re-immerging infection can widely spread by mosquito bites and cause serious complications in a central nervous system among children born to infected mothers. Thus, they should be protected. This study aims to (1) To determine the prevalence of neutralizing ZIKV antibodies in the post-outbreak areas among the general population and pregnancy women residing at various distances from the houses of the nearest index patients; (2) To examine the cross-neutralizing capacity of antibodies against ZIKV on other flaviviruses commonly found in the study areas; (3) To identify factors associated with the presence of neutralizing ZIKV antibodies. Methods The two post-outbreak communities were visited at 18 months after the outbreaks. We enrolled (1) 18 confirmed ZIKV infected (index) cases, (2) sample of 554 neighbors in the outbreak areas who lived at various distances from the index patients’ houses, (3) 190 residents of non-outbreak areas, and (4) all pregnant women regardless of gestational age residing in the study areas (n = 805). All serum specimens underwent the plaque reduction neutralization test (PRNT). Ten randomly selected ZIKV seropositive and ten randomly selected seronegative specimens were tested for dengue virus serotypes 1–4 (DENV1–4) and Japanese encephalitis virus (JEV) antibodies using PRNT90. Serum titer above 1:10 was considered positive. Multiple logistic regression was used to assess factors associated with seropositivity. Results Out of all 18 index cases, 9 remained seropositive. The seroprevalence (95% CI) in the two outbreak areas were 43.7% (35.9–51.6%) and 29.7% (23.3–36.0%) in general population, and 24.3% (20.1–28.8%) and 12.8% (9.7–16.5%) in pregnant women. Multivariate analysis showed that seropositivity was independent of the distance gradient from the index’s houses. However, being elderly was associated with seropositivity. DENV1–4 and JEV neutralizing antibodies were present in most ZIKV-positive and negative subsamples. Conclusion Protective herd immunity for ZIKV infection is inadequate, especially among pregnant women in the two post-outbreak areas in southern Thailand.

Seroprevalence of Zika Virus in Amphawa District, Thailand, after the 2016 Pandemic

“…We developed ZIKV NS1 ELISA and achieved comparable results with the globally available NS1 BOB ELISA, including minimal cross-reactivity with other flaviviruses. Using our ZIKV NS1 ELISA and cutoff criteria, the seroprevalence after the outbreak (i.e., Day 0) was much lower than that reported in other studies [ 22 , 23 , 24 , 25 , 26 ]. We also observed an increase in ZIKV NS1 seroprevalence throughout the age groups, which was consistent with prior findings [ 27 ].…”

“…However, the interpretation was difficult because of high cross-reactivity between ZIKV and other dengue virus serotypes. Recent studies in Thailand also demonstrated cross-reactivity between neutralizing antibodies against ZIKV and all four dengue virus serotypes [ 25 , 26 ]. Therefore, PRNT may not be an appropriate tool to confirm ZIKV infection in dengue-endemic areas.…”

Characteristics, risk factors, and outcomes related to Zika virus infection during pregnancy in Northeastern Thailand: A prospective pregnancy cohort study, 2018–2020

“…A report of ZIKV seroprevalence in pregnant women attending antenatal care clinics in one hospital from May to October 2019 in Bangkok, Thailand, revealed that approximately 60% of pregnant Thai women did not have detectable levels of neutralizing antibodies against ZIKV [ 84 ]. Similarly, a post-outbreak study conducted in two communities in Southern Thailand also reported a low prevalence (12.8%) of ZIKV neutralizing antibodies in pregnant women [ 85 ]. Continued surveillance for adverse infant outcomes and neurodevelopmental delays among children would support estimating the burden of congenital ZIKV infections in Southeast Asia.…”