The large study found that older children, mainly teens and tweens, are more likely to spread the virus than young children or adults, as Bloomberg reported. That means that kids going to high school and middle school are likely to pass the virus amongst each other and then bring it home, even if they do not have any symptoms.

The findings suggest that as schools reopen, communities will start to see clusters of infection take root that include children of all ages, several experts told The New York Times.

"I fear that there has been this sense that kids just won't get infected or don't get infected in the same way as adults and that, therefore, they're almost like a bubbled population," said Michael Osterholm, an infectious diseases expert at the University of Minnesota.

To conduct the study, researchers from the South Korea Centers for Disease Control and Prevention studied contact tracing reports from 59,073 contacts of 5,706 COVID-19 patients, as The New York Post reported. The scientists found that that kids nine years old and younger had much lower rates of transmitting the virus in their households.

For people who lived with patients between the ages of 10 and 19, 18.6 percent tested positive for the virus within about 10 days after the initial case was detected. That was the highest rate of transmission among the groups studied, according to Bloomberg. Children younger than 10 spread the virus at the lowest rate, clocking in at a 5.3 percent transmission rate, though researchers warned that could change when schools reopen.

"Rates were higher for contacts of children than adults," they study authors wrote, as The New York Post reported. "These risks largely reflected transmission in the middle of mitigations and therefore might characterize transmission dynamics during school closure."

The study was rigorous and through, as it indexed patients by age (0–9, 10–19, 20–29, 30–39, 40–49, 50–59, 60–69, 70–79, and > 80 years). Amongst those groups, the households with someone in the 10-19 range had the highest rate of infection spread to other household contacts, according to the study. However, there was a limitation since those infected are less likely than adults to show symptoms, so the study may have underestimated the number of children who set off the chain of transmission within their households, according to The New York Times.

It also found that the most common spread of the virus was between household contacts, as Science Alert reported.

"Higher household than non-household detection might partly reflect transmission during social distancing, when family members largely stayed home except to perform essential tasks, possibly creating spread within the household," the researchers explained in their study, according to Science Alert.

As The New York Times pointed out, several studies from Europe and Asia have suggested that young children are less likely to get infected and to spread the virus. But most of those studies were small and flawed, said Dr. Ashish Jha, director of the Harvard Global Health Institute.

The new study "is very carefully done, it's systematic and looks at a very large population," Dr. Jha said to The New York Times. "It's one of the best studies we've had to date on this issue."