NIAID Now | October 08, 2019
As Zika virus spread across the Americas in 2015 and 2016, public health authorities became alarmed by the increasing number of cases of microcephaly and other fetal abnormalities attributed to Zika virus infection in utero. However, it was unknown whether the virus could also impact the development of young children infected after birth. In a study that began in 2017 in Guatemala, NIAID-supported researchers have been studying sets of mothers and their children who might have been exposed to the Zika virus. Their preliminary results indicate that the virus likely has little or no impact on the neurological development of children who were infected after birth.
Aspects of the study were presented at IDWeek in both an oral presentation and a poster session by one of the co-principal investigators, Flor M. Munoz, M.D. of Baylor College of Medicine in Houston, Texas. Edwin J. Asturias, MD is the co-principal investigator from the University of Colorado, in Denver, Colorado. The study, conducted by researchers in both Guatemala and the United States, is funded by NIAID.
The full study enrolled 374 children between one and five years old, 500 infants, and 497 mothers in Guatemala, in an area where the related dengue virus is endemic and the Zika virus has been found. Upon enrolling, the volunteers received blood tests to see if they had been exposed to either dengue, Zika, or both. The study began approximately two years after the virus was first detected in Guatemala, so researchers were able to safely assume that older children who showed serological evidence of prior infection likely became infected after they had been born. The scientists meticulously tested the infants’ and children’s early learning abilities, both when they first enrolled in the study, and over a 12 month period of time.
Like other research studies that began in response to the arrival of Zika virus in the Americas, the study faced many challenges. Because Zika infection may be asymptomatic, and the outbreak was already dwindling as the study began, the researchers have been unable to confirm children with active Zika infections. However, 25 percent of all children under 5 years of age had serological evidence of prior exposure to the Zika virus. In addition, although the infants in the study performed well on neurological tests, older children generally had lower developmental scores than their U.S. counterparts—possibly due to reasons including fewer educational resources, malnutrition, or other confounding factors.
However, among children ages 1-5 years old, who could only have been exposed to the Zika virus after birth, the researchers found that prior infection with the Zika virus did not lower their neurodevelopmental test scores. This finding supports theories that children are less vulnerable to Zika’s neurodevelopmental effects if infected after birth. However, the researchers recognize the limitations of this study, including the need to conduct follow up for neurologic and neurodevelopmental outcomes over a longer period of time.
This research is the first to study the impact of Zika virus infection in children in such detail. While the researchers still need to complete a full analysis of the samples and test results that they collected before making final conclusions, the research that they completed in Guatemala provides a firm groundwork for future studies.