The top US health body has issued new guidelines on the reopening of schools, clearly weighting its recommendations in favor of having students return to their classrooms in fall.
The updated advice from the Centers for Disease Control and Prevention (CDC) was posted Thursday night, and came a few weeks after President Donald Trump asked the agency to change course.
"We owe it to our nation's children to take personal responsibility to do everything we can to lower the levels of COVID-19, so they can go back to school safely," CDC chief Robert Redfield said Friday.
With the virus still rampant in many parts of the country, a number of cities including Houston and Los Angeles have already announced that schools will reopen virtually.
Others like New York, where the epidemic has receded, are opting for a hybrid model.
Although the CDC says schools must take into consideration local virus transmission rates, it offers no precise guidance on what the cut-off threshold should be.
Asked by a reporter how he would define a hotspot that should not yet reopen its schools, Redfield said: "Right now we're looking where the percent positivity rate within the community is greater than five percent."
Positivity refers to the rate of coronavirus tests that come back positive, and the World Health Organization (WHO) considers a rate of above five percent to indicate rampant community spread.
Officials will be looking at data on the county level, but as a gauge, only 17 states plus the US capital currently fulfill this requirement on a statewide basis.
Redfield however stressed it was "just guidance to consider, to be more cautious."
- Benefits and risks -
The scientific community's position on schools reopening isn't completely clear cut.
On one side, the risk of children becoming seriously ill from COVID-19 is low, while pediatricians emphasize the beneficial role schools play in children's social development and mental health.
Some children have developed what doctors are calling multisystem inflammatory syndrome (MIS-C) after exposure to SARS-CoV-2.
Most have recovered from this post-viral illness, though a handful have died.
The US also has the benefit of being able to draw on other countries' experience.
Some countries which have been able to bring down their epidemics have reopened schools without major problems, while others like Israel saw spikes.
Finally, there are other benefits of in-person learning.
According to the CDC, prolonged school closures could worsen achievement gaps across income levels and racial and ethnic groups.
A study of 800,000 students by researchers at Brown and Harvard universities looking at how an online math program called Zearn was used found that student progress decreased throughout late April, particularly in low-income areas.
- Disease carriers? -
But the issue isn't just about whether children can get seriously ill -- it's whether they can become disease vectors themselves for their families and wider communities.
According to the CDC's latest advice just posted on its website, "the best available evidence" that has emerged so far "suggests that children are unlikely to be major drivers of the spread of the virus."
However, this does not correspond with the latest notable study on the matter which was published last week in the CDC's own journal of Emerging Infectious Diseases.
The study, conducted in South Korea, showed children younger than 10 transmit to others much less often than adults do -- but those between the age 10 and 19 can spread the virus just as well as adults.
"I think we need to start off with a little humility and say, 'We don't know all the answers to that right now,'" Anthony Fauci, the country's top infectious disease expert said, invoking the study.
Speaking in a video chat hosted by the Center for Strategic & International Studies, Fauci said more research was needed -- particularly on the question of how easily children get infected compared to adults.
The National Institutes for Health is studying this question and hopes to have results by December, he added.
US health authorities are urging schools to reopen to students in the fall -- here, school buses are seen in San Francisco