Youth sports are helping to fuel the worrisome rise in COVID-19 cases among young people, the head of the CDC said Monday.

“We are learning that many outbreaks in young people are related to youth sports and extracurricular activities,’’ Dr. Rochelle Walensky, the federal agency’s director, said at a White House briefing.

“This is among 18- to 24-year-olds where we’re actually seeing some peaks in cases,” she said. “Cases are increasing nationally, and we’re seeing this predominantly in younger adults.”

Walensky noted that Centers for Disease Control and Prevention guidance is for youth sports to be “limited,” but added that if they are not, outbreaks can still be contained with a testing regimen.

The latest daily average of new US hospitalizations in the past week is 4,970, she said — up 3 percent from the daily average during the previous seven-day period.

She said it is still unclear whether the virus’s more transmissible variants may be behind the increase in COVID-19 among young people.

“We don’t yet have evidence to say,” Walensky said.

She suggested that the vaccination of younger people would have “a massive impact’’ on them transmitting the virus.

Currently, those under 16 years of age are not eligible for the vaccine in the US.

Vaccine-maker Pfizer announced earlier this month that a clinical trial it recently conducted among 2,260 US adolescents showed its inoculation is 100 percent effective in kids ages 12 to 15 — suggesting children could get preventative shots as soon as before the next school year.

Last month, New York Gov. Andrew Cuomo lifted the state’s ban on even high-coronavirus-risk school sports.