The Rio Seroprevalence Study was the first combined seroprevalence study of ZIKV, CHIKV and DENV in the state of Rio de Janeiro following the 2015 and 2016 epidemics using accurate flavivirus serology. Results reflect the scale of infection with 13% of the population infected with ZIKV in each of the two epidemic seasons. Nonetheless, most of the adult population studied was seronegative for ZIKV and CHIKV at the end of 2016. Data also demonstrate that the acquisition of ZIKV and CHIKV infection was associated with lower socio- economic status in this population. Herd immunity may have played a role in the subsequent decrease in Zika virus cases seen in Rio from 2016 to 2021.
The Seroprevalence Study in Jamaica investigated the seroprevalence of ZIKV, CHIKV and DENV in an antenatal population in Kingston, Jamaica, using maternal samples (sera from 584 pregnant women enrolled in the Jamaica VT Study). Samples were tested using Euroimmun ZIKV IgG, Euroimmun CHIKV IgG, and Panbio DENV IgG ELISA assays. Further work was done using the more specific BNITM (Hamburg) ZIKV IgG assay.
The retrospective serological study of mother / baby pairs in Salvador, Brazil looked at sequential paired sera from a mother-baby cohort collected as part of a previous study in Instituto Gonçalo Moniz/Fiocruz in Salvador, Bahia during and after the ZIKV epidemic. Sera routinely collected were tested using Euroimmun ZIKV IgM and IgG assays. Sera was then collected from mother / baby pairs together with control population sera and tested with BNITM ZIKV IgM and IgG assays and combined / compared with the Euroimmun ZIKV IgG EIA results obtained during the epidemic. The study provided some of the first results of ZIKV seroprevalence in the population of Salvador and Brazil.
ZIKAction contributed to the Birth cohort study on Prevalence and incidence of DENV and ZIKV infection in an urban area in Rio de Janeiro on ZIKV infection 2013-2018 nin a high-risk favela community in the north of Rio. In summary, in this cohort of young children, infection with ZIKV was low during 2015-2018 and that most of the tested children (97.4%) remain susceptible to ZIKV infection. In the group of 23 women with PCR-confirmed ZIKV infection in pregnancy, no evidence of persisting ZIKV IgG antibody was found in their children indicating either no vertical transmission, or that persisting IgG antibody is not a useful marker of congenital ZIKV (as has been true for other congenital infections such as rubella). The contrast in the burden of infection in this population between DENV and ZIKV is striking. Studies in the adult population of Rio (earlier in this report) show an exposure of 39% to ZIKV over a similar period and the PCR confirmed case in this community indicate the virus was circulating.
Other work included seroprevalence studies of ZIKV, DENV and CHIKV in adults, pregnant women and children in Brazil and Jamaica, plus a study of the metabolomic profiles of ZIKV-exposed infants, which showed significant changes in the plasma lipidome in exposed versus control newborns. A study of the metabolomic profiles of ZIKV-exposed infants, showed significant changes in the plasma lipidome in exposed versus control newborns.