By Stephanie Stahl

PHILADELPHIA (CBS) — After preying heavily on the elderly in the spring, the coronavirus is increasingly infecting American children and teens in a trend, authorities say, appears driven by school reopenings and the resumption of sports, playdates and other activities. There’s been a sudden and dramatic increase in COVID-19 cases among children, according to new research released by the American Academy of Pediatrics.

The Centers for Disease Control and Prevention is also reporting a spike in cases among college-age students.

The CDC says the sharpest increase in COVID-19 cases among 18- to 22-year-olds is in nine northeastern states, including Pennsylvania and New Jersey.

That was expected with the reopening of some colleges, but more than half of people that age group does not attend college and for younger children, they now account for 10% of all cases.

Almost 625,000 children in the United States have contracted the coronavirus since the start of the pandemic, according to a new study from the Academy of Pediatrics. It says there’s been a sudden and alarming increase.

In the beginning of April, kids accounted for 2% of all positive COVID results. By September, they were over 10%.

“During that time period is when we had college outbreaks across the country and maybe the college-age students are likely to be in contact with younger siblings, or maybe some of them fell in as pediatric cases themselves and that was connected to that wave,” said Philadelphia Health Commissioner Dr. Thomas Farley.

There has also been a sharp increase in coronavirus in people between the ages of 18 to 22, mainly in the northeast.

In announcing new metrics for reporting cases in Philadelphia, Dr. Farley said new COVID-19 infections continue to come from spread among family members and small gatherings.

“In schools, fortunately, we are not seeing any clusters of infections in any of the kindergarten through 12 schools that are open so far,” Dr. Farley said.

Pennsylvania has just over 8,000 COVID-19 cases among 5- to 18-year-olds and even though most don’t get seriously sick, children are not immune.

“We’ve heard that all over the place, that children don’t get infected, that they’re that they don’t spread disease. And we know that’s not true. So, having said that, however, children are less likely to be infected with symptoms than adults,” said pediatrician, Dr. Yvonne Maldonado.

The new research also revealed that 58% of children with COVID-19 infections had at least one symptom of the virus, but only 5% had no symptoms.

Stephanie Stahl