EVIDENCE SUGGESTS KIDS TRANSMIT VIRUS
Researchers say school closures could slow spread
Among the most important unanswered questions about COVID-19 is this: What role do children play in keeping the pandemic going?
Fewer children seem to get infected by the coronavirus than adults, and most of those who do have mild symptoms, if any. But do they pass the virus on to adults and continue the chain of transmission?
The answer is key to deciding whether and when to reopen schools, a step that President Donald Trump urged states to consider before the summer.
Two new studies offer compelling evidence that children can transmit the virus. Neither proved it, but the evidence was strong enough to suggest that schools should be kept closed for now, many epidemiologists who were not involved in the research said.
Many other countries, including Israel, Finland, France, Germany, the Netherlands and the United Kingdom have all either reopened schools or are considering doing so in the next few weeks.
In some of those countries, the rate of community transmission is low enough to take the risk. But in others, including the United States, reopening schools may nudge the epidemic’s reproduction number — the number of new infections estimated to stem from a single case, commonly referred to as R0 — to dangerous levels, epidemiologists warned after reviewing the results from the new studies.
In one study, published last week in the journal Science, a team analyzed data from two cities in China — Wuhan and Shanghai — and found that children were about onethird as susceptible to coronavirus infection as adults. But when schools were open, they found, children had about three times as many contacts as adults and three times as many opportunities to become infected, essentially evening out their risk.
Based on their data, the researchers estimated that closing schools is not enough on its own to stop an outbreak, but it can reduce the surge by about 40 to 60 percent and slow the epidemic’s course.
“My simulation shows that yes, if you reopen the schools, you’ll see a big increase in the reproduction number, which is exactly what you don’t want,” said Marco Ajelli, a, epidemiologist who did the work while at the Bruno Kessler Foundation in Trento, Italy.
The second study, by German researchers, was more straightforward. The team tested children and adults and found that children who test positive harbor just as much virus as adults do — sometimes more — and so, presumably, are just as infectious.
“Are any of these studies definitive? The answer is ‘No, of course not,’ ” said Jeffrey Shaman, an epidemiologist at Columbia University who was not involved in either study. But, he said, “to open schools because of some uninvestigated notion that children aren’t really involved in this, that would be a very foolish thing.”
The German study was led by Christian Drosten, a virologist who has ascended to something like celebrity status in recent months for his candid and clear commentary on the pandemic. Drosten leads a large virology lab in Berlin that has tested about 60,000 people for the coronavirus. Consistent
with other studies, he and his colleagues found many more infected adults than children.
The team also analyzed a group of 47 infected children between ages 1 and 11. Fifteen of them had an underlying condition or were hospitalized, but the remaining were mostly free of symptoms. The children who were asymptomatic had viral loads that were just as high or higher than the symptomatic children or adults.
In the China study, the researchers created a contact matrix of 636 people in Wuhan and 557 people in Shanghai. They called each of these people and asked them to recall everyone they’d had contact with the day before. They defined a contact as either an in-person conversation involving three or more words or physical touch such as a handshake and asked for the age of each contact as well as the relationship to the survey participant.
Comparing the lockdown with a baseline survey from Shanghai in 2018, they found that the number of contacts during the lockdown decreased by about a factor of seven in Wuhan and eight in Shanghai.
“There was a huge decrease in the number of contacts,” Ajelli said. “In both of those places, that explains why the epidemic came under control.”
They also estimated that closing schools can lower the reproduction number — again, the estimate of the number of infections tied to a single case — by about 0.3; an epidemic starts to grow exponentially once this metric tops 1.
In many parts of the United States, the number is already hovering around 0.8, Ajelli said.
However, some other experts noted that keeping schools closed indefinitely is not just impractical but also may do lasting harm to children. Jennifer Nuzzo, an epidemiologist at Johns Hopkins University’s Bloomberg School of Public Health, said the decision to reopen schools cannot be made based solely on trying to prevent transmission.
“I think we have to take a holistic view of the impact of school closures on kids and our families,” Nuzzo said. “I do worry at some point, the accumulated harms from the measures may exceed the harm to the kids from the virus.”