Study examines how kids in households can spread virus
Babies and toddlers are less likely to bring the coronavirus into their homes than teenagers are, but once they are infected, they are more likely to spread the virus to others in their households, according to a large new study by a Canadian public health agency.
The findings can be explained, at least in part, by behavioral factors, experts said, including the fact that very young children require lots of hands-on care and cannot be isolated when they are sick.
The study, which was published in the journal JAMA Pediatrics on Monday, does not resolve an ongoing debate over whether infected children are as contagious as adults, and it does not suggest that toddlers are driving the pandemic. But it demonstrates that even very young children can still play a role.
“This study showed that even the youngest of children readily transmit the virus,” said Zoe Hyde, a public health researcher at the University of Western Australia, who was not involved in the research.
She added: “The key takeaway for me is that it clearly shows that there’s transmission from children occurring in the household. This means we urgently need to think about how we’re going to protect schools when they reopen shortly.”
During the early months of the pandemic, some scientists suggested that young children, in particular, rarely got infected with or transmitted the virus. But those observations may have been distorted by the fact that most children had few social encounters during that time.
“I think they were biased by the fact that children were sequestered at home,” said Dr. Tina Hartert, a respiratory
researcher at Vanderbilt University, who was not involved in the new study. “They were recommended not even to play with neighbors, they didn’t go to school, they didn’t go to day care.”
The new study, which was conducted by researchers at Public Health Ontario, is based on records of COVID-19 cases and positive coronavirus tests in Ontario from June 1 to Dec. 31, 2020.
They focused on 6,280 households in which the first person to catch the virus was under 18. Then they looked for secondary cases, or others in the same home who got sick in the two weeks after the first child fell ill.
In most cases, they found, the chain of transmission stopped with the infected child, but in 27.3% of households, children passed the virus along to at least one other resident.
Adolescents were most likely to bring the virus into the home: Children ages 14-17 made up 38% of all the index cases. Children ages 3 or younger were the first to get sick in just 12% of households — but they were the most likely to spread the virus to others in their
homes. The odds of household transmission were roughly 40% higher when the infected child was 3 or younger than when they were 14-17.
The findings may be the result of behavioral differences between toddlers and teens, medical experts said.
“When we think about what’s teen social behavior outside of the house, they’re spending a lot of time together, they’re often in quite close quarters, they’re often touching or sharing a drink,” said Dr. Susan Coffin, an infectious disease specialist in Philadelphia, who was not involved in the study.
Those behaviors could make teens more likely to contract the virus and bring it home, she said.
On the other hand, while very young children probably have less social interaction outside the home, they tend to be in close physical contact with others in their households, in addition to frequently putting their hands and other objects in their mouths, which could help spread the virus. “Once they bring it into the household, it can be spread easily,” Coffin said.