These older children are frequently as big as adults, and yet may have some of the same unhygienic habits as young children do. They may also have been more likely than the younger children to socialize with their peers within the high-rise complexes in South Korea.
“We can speculate all day about this, but we just don’t know,” Dr. Osterholm said. “The bottom line message is: There’s going to be transmission.”
He and other experts said schools will need to prepare for infections to pop up. Apart from implementing physical distancing, hand hygiene and masks, schools should also decide when and how to test students and staff — including, for example, bus drivers — when and how long to require people to quarantine, and when to decide to close and reopen schools.
But they face a monumental challenge because the evidence on transmission within schools has been far from conclusive so far, experts said. Some countries like Denmark and Finland have successfully reopened schools, but others, like China, Israel and South Korea, have had to close them down again.
“People, depending on their ideology on school opening, are choosing which evidence to present — and that needs to be avoided,” said Jeffrey Shaman, an epidemiologist at Columbia University’s Mailman School of Public Health in New York.
Although the new study does not offer definitive answers, he said, it does indicate that schools can increase virus levels within a community.
“So long as children are not just a complete dead end — incapable of passing the virus on, which does not seem to be the case — putting them together in schools, having them mix with teachers and other students will provide additional opportunities for the virus to move from person to person,” he said.