Serious complications are rare among children infected with the Zika virus after birth, federal health researchers concluded in a study published on Friday — a rare bright spot in the unfolding story of the epidemic.

About 160 teenagers and toddlers infected with Zika virus have been reported to the Centers for Disease Control and Prevention since 2015. The agency’s new study marks the largest survey yet of laboratory-confirmed cases in children.

All of the infections were the result of travel, most commonly to the Dominican Republic and Puerto Rico. About 100 of the cases occurred in June and July alone. The report represents just a fraction of the actual number of children in the continental United States infected with Zika.

The children, aged 1 month to 17 years, were initially identified because they had symptoms of infection; only those who became ill were included in the research. Yet most people who are infected have no symptoms at all.