DENVER -- A highly contagious stomach virus is spreading to thousands of kids across the metro area, doctors say, and it's happening right before school starts.

"In the middle of the night, I woke up because my stomach really hurt. It felt like someone was down there punching me," said Christopher Jenkins, 12, who missed two days of rehearsal during the Rocky Mountain Theater for Kids summer camp.

Jenni Greenwald, 15, had a similar experience.

"After dinner, I felt really sick, and then I barfed my guts out," she said.

The virus moved fast through the camp.

In about a week, at least 15 young actors had to miss camp, and they were worried the show might be canceled.

Dr. Joe Craig, medical director at the Rocky Mountain Youth Clinics, said the kids aren't just being dramatic.

His clinics have seen a summer spike in a stomach bug, and doctors are worried it will spread further when school starts.

"Some of the strains are just worse. It's a newer strain that nobody's really seen. Nobody's intestines have seen it yet, so they get sicker with it," said Craig.

Some children have even been hospitalized, he said.

But most kids are singing again within a few days at the theater camp.

"If you get it, that sucks, but it's out quick," said Greenwald.

And as quick as it is "out," the kids are back on stage.

After all, the show must go on.

Doctors said parents and school officials should take extra precautions by reminding kids to wash their hands and use sanitizer, and when the symptoms are at their worst, keep children at home.