As the debate continues over whether children should return to school this fall, the coordinator of the White House's coronavirus task force says it's "still an open question" how much children under 10 spread the illness.
"We know that children under 18 are less sick, but there are some that suffer terrible consequences if they have underlying conditions," Dr. Deborah Birx told Savannah Guthrie on TODAY Friday. "What I can't tell you for sure despite the South Korea study is whether children under 10 in the United States don't spread the virus the same as children over 10.
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"I think that is still an open question that needs to be studied in the United States. We certainly know from other studies that children under 10 do get infected, it's just unclear how rapidly they spread the virus."
In the large study in South Korea referenced by Birx, children younger than 10 were found to transmit the virus less than adults, and those between 10 and 19 were found to spread it as much as adults. However, the study indicated that children under 10 do spread the virus, so the risk is not zero.
The study analyzed reports 5,706 people who reported COVID-19 symptoms between Jan. 20 and March 27 and the 59,073 contacts identified by tracing from those initial "index patients."
A district of 2,000 students in Alcoa, Tennessee, has already resumed in-person classes one day a week with precautions like daily temperature checks, staggered attendance, smaller classes and mask use for students and teachers.
Birx's comments also came after the Centers for Disease Control and Prevention released guidelines on Thursday for reopening schools with an emphasis on a return to the classroom. President Donald Trump has also pushed for a full return to in-person learning, threatening to remove funding for schools that don't reopen their classrooms.
Trump said Wednesday that he would be "comfortable" sending his 14-year-old son and school-age grandchildren back to school this fall, saying that children "have very strong immune systems."
He again spoke about his stance on a full reopening in a briefing on Thursday.
"I hope that local leaders put the full health and well-being of their students first and make the right decision for parents, teachers and not make political decisions. This is about something very, very important," Trump said.
Birx emphasized school districts using the new CDC guidelines to analyze the steps they need to take to reopen.
"Knowledge is power, and I think why that was very important that the president yesterday had the map behind him showing where the most recent cases are," Birx said. "Those were the cases over the last seven to 14 days really to inform the public there are areas in the United States where cases are rapidly increasing and continue to increase.
"And in those cases and with the new CDC guidelines to really give parents, school administrators, teachers and the county supervisors really an understanding of where they are in the epidemic and what precautions they need to take."
Two of California's largest school districts have already announced that classes will be online-only in San Diego and Los Angeles in the fall. New York City has announced hybrid models mixing a few days a week of in-person learning with online instruction, while Florida's largest teachers union has filed a lawsuit against the state over the government's reopening order.
Birx stressed vigilance across the country in adhering to wearing masks, social distancing and washing your hands in slowing the spread of the virus. Trump tweeted a photo of himself wearing a mask this week after months of downplaying face coverings.
"This is a signal to the American people that we have to change our behavior now before this virus completely moves back up through the north," she said.