Seroprevalence of Dengue, Chikungunya and Zika at the epicenter of the congenital microcephaly epidemic in Northeast Brazil: a population-based survey

Abstract

Background The Dengue viruses (DENV) serotypes 1, 2, 3 and 4 were re-introduced in the Northeast Brazil from the 1980’s until 2010’s. Zika (ZIKV) and Chikungunya (CHIKV) viruses were introduced around 2014 and caused large outbreaks in 2015 and 2016. However, the true extent of the ZIKV and CHIKV outbreaks and the risk factors associated with exposure remain vague. Methods We conducted a stratified multistage household serosurvey among residents aged between 5 and 65 years in the city of Recife, Northeastern Brazil, from August 2018 to February 2019. The city neighborhoods were stratified according to high, intermediate, and low socioeconomic strata (SES). Previous ZIKV, DENV and CHIKV infections were detected by IgG based enzyme linked immunosorbent assays (ELISA) . Recent ZIKV and CHIKV infections were assessed through IgG3 and IgM ELISA, respectively. Design-adjusted seroprevalence were estimated by age group, sex, and SES. The ZIKV seroprevalence was adjusted to account for the cross-reactivity with dengue. Individual and household-related risk factors were analyzed through regression models to calculate the force of infection. Odds Ratio (OR) were estimated as measure of effect. Principal findings A total of 2,070 residents were investigated. The forces of infection for high SES were lower for all three viruses as compared to low SES. Overall, DENV seroprevalence was 88.7% (CI95%:87.0-90.4), (81.2% (CI95%:76.9-85.6) in the high SES and 90.7% (CI95%:88.3-93.2) in the low). The overall adjusted ZIKV seroprevalence was 34.6% (CI95%:20.0-50.9), (47.4% (CI95%:31.8-61.5) in the low SES and 23.4% (CI95%:12.2-33.8) in the high). CHIKV seroprevalence was 35.7% (CI95%:32.6-38.9), (38.6% (CI95%:33.6-43.6) in the low SES and 22.3% (CI95%:15.8-28.8) in the high). ZIKV seroprevalence increased with age while CHIKV seroprevalence was almost constant through age. The serological markers of recent infections for ZIKV and CHIKV were 1.5% (CI95%:0.1-3.7) and 3.5% (CI95%:2.7-4.2) respectively. Conclusions Our results confirmed continued DENV transmission and intense ZIKV and CHIKV transmission during the 2015/2016 epidemics followed by ongoing low-level transmission. The study also highlights that a significant proportion of the population is likely still susceptible to be infected by ZIKV and CHIKV, raising questions on herd immunity and antibody detection thresholds and the reasons underlying cease of the ZIKV epidemic in 2017/18.