While the study didn’t measure transmissibility, it raises questions — just as schools start to reopen — about how easily the new coronavirus may be spread by the under-5 set.

“We had just noticed that some of the children that we were testing for SARS CoV-2 that were positive, the youngest children seemed to have a high amount of the viral nucleic acid — a high viral load in their nose — compared to some of our older children and adults,” lead author Dr. Taylor Heald-Sargent, a pediatric infectious diseases specialist at Lurie Children’s Hospital of Chicago, told CNN. “And so when we … actually ran the numbers, controlled for a few things, we found that there was actually a statistically significant higher amount of the genes that are encoded by SARS, which usually correlates to more virus, in the nose of children less than five years old, compared to older children and adults.”