That estimate of 10% to 15% is based, in part, on the testing rates of other countries compared to the U.S., Lover said.

“There’s a lot of data in Italy that shows people with mild symptoms can still spread coronavirus easily, so it’s important for those people to be tested,” he said. “You need to see if they have it and minimize their social contacts to slow the spread.”

About 10% of all cases are being reported, said Thomas McAndrew, also at UMass Amherst’s School of Public Health and Health Sciences. He has been aggregating data from experts’ models.

“It looks like tenfold the cases being reported now,” McAndrew said.