In most cases, the chain of transmission ended with the infected child, but in 27.3 percent of households, children passed the virus on to at least one other resident.
Aug 16, 2021, 1:10 p.m. ET
Young people were most likely to bring the virus into the home: children aged 14 to 17 made up 38 percent of all index cases. Children who were 3 or younger were the first to get the disease in only 12 percent of households – but they were most likely to spread the virus to others in their homes. The likelihood of household transmission was about 40 percent higher if the infected child was 3 years or younger than if they were between 14 and 17 years old.
The results could be due to behavioral differences between toddlers and teenagers, medical experts said.
“When we think about what the social behavior of teenagers outside the home is, they spend a lot of time together, are often confined, often touching or sharing a drink,” said Dr. Susan E. Coffin, an infectious disease specialist at Philadelphia Children’s Hospital who was not involved in the study.
These behaviors could lead teenagers to contract the virus and bring it home, she said.
On the other hand, while very young children are likely to have less social interactions outside of the home, they tend to be in close physical contact with others in their household and, in addition, frequently put their hands and other objects in their mouths, which contributes to the spread could be the virus. “Once they get it into the household, it can be easily spread,” said Dr. Coffin.
It’s also possible that the youngest children have higher levels of virus in them or have higher levels of virus shedding than teenagers, the researchers found. Some studies have shown that although young children rarely become seriously ill, they can carry similar or even higher levels of the virus than adults. Although viral load is not a perfect predictor of infectivity, the data suggest that children may be as contagious as adults.
But the dynamics of disease transmission are complex, and the exact role children play in spreading the virus remains uncertain.