Omar Zepeda is a PhD student studying at the University of Costa Rica and a fellow of the Nicaraguan Emerging and Endemic Diseases (NEED) program. He is mentored by Filemon Bucardo, PhD. At the recent 4th Annual Global Health Symposium Zepeda presented his findings on the Zika and Dengue viruses focusing on infant and maternal antibody dynamics. In Nicaragua, families live with the daily reality of viruses like Zika and Dengue, and the risks are especially high during pregnancy and a baby’s first year of life.
Zepeda presented a longitudinal study where researchers followed pregnant women and their babies to understand how these infections and the immune response to them present over time. Additionally, his team conducted a study on acute dengue cases, to better categorize disease progression and evaluate the role of pre-exiting immunity.
During the 2017 Zika epidemic, about 55% of pregnant women showed evidence of Zika infection, and around 21% were infected during pregnancy itself. Roughly 17% of births had some type of adverse outcome, but only 1.5% of infants met the criteria for congenital Zika syndrome. The timing of infection during pregnancy did not clearly predict which babies would have complications, challenging early assumptions about trimester-specific risks.
The study also examined how long maternal antibodies protect infants. They found that Zika antibodies persisted in most mothers for at least two years. However, babies lost most of that protection by 6–9 months of age, creating a vulnerable window in a setting where Dengue is endemic. Another observation from this study is that IgG3 levels were higher than the IgG1 level. This is a naturally maternal antibody transfer when IgG1 is typically the dominant subclasses. Because Zika and Dengue antibodies cross-react, some rises in Zika antibodies in older infants were driven by Dengue infections, complicating diagnosis and vaccine decision-making.
Looking at a 2022 Dengue outbreak, the team found that most cases occurred in children with prior Dengue exposure, while past Zika infection did not appear to increase Dengue disease risk. Using insights from prenatal data, the team built a practical algorithm to better identify Zika infections during pregnancy and improve serological surveillance in resource-limited, Dengue-endemic settings.
Together, these findings highlight how maternal immunity, viral cross-reactivity, and population history all shape which children are most at risk—and how public health strategies can better protect them.