NEW YORK — A first look at U.S. teens and young children who were infected with Zika suggests the virus typically causes at worst only a mild illness.

Zika infection during pregnancy can cause severe brain-related birth defects.

But the report seems to confirm health officials' belief that infections after birth in children are similar to infections in adults — most people don't feel sick, and some develop only mild symptoms like fever, rash, joint pain and red eyes.

But some experts say there are not enough data to answer questions about the virus' potential impact on the developing brains of infants and small children.

The report, released Friday by the Centers for Disease Control and Prevention, is based on 158 infections this year in kids aged 1 month to 17 years.

All the children picked up the virus while traveling abroad, and the bulk of them were older kids in their teens.

Only 16 were age 4 or younger and only four were under a year old.

Experts are worried about young children because they can be more severely affected by infections in general, and because their brains are developing rapidly.

“I'm really concerned about birth through the first birthday,” said Dr. Carrie Byington, a University of Utah researcher who focuses on infections in children.

None of the children studied died, and none developed a paralyzing condition seen in some infected adults called Guillain-Barre syndrome.

But Guillain-Barre is rare, seen only once in every several thousand Zika illnesses in adults.

It may be that kids can still get it, but there weren't enough cases for it to surface, said Dr. Ganeshwaran Mochida, a pediatric neurologist at Boston Children's Hospital.