While children were the least affected by the Covid-19 disease, a study shows that 70.4 percent of nearly 850,000 US household transmissions of the SARS-CoV-2 virus originated with a child. The study, published in JAMA Network Open, showed that young children were more likely to spread the virus. A team led by researchers at Boston Children’s Hospital provided smartphone-attached thermometers to 848,591 families with 1,391,095 members, taking 23,153,925 temperature readings from October 2019 to October 2022.
Fevers were a proxy for infection. Of the 166,170 households with both adult and child participants (51.9 percent of households with multiple participants), there were 516,159 participants, of whom 51.4 percent were children.
In these households, 38,787 infections occurred, of which 40.8 percent were child-to-child, 29.6 percent child-to-adult, 20.3 percent adult-to-child, and 9.3 percent adult-to-adult. The median sequence interval between index and secondary cases was two days.
70.4 percent of all household broadcasts began with a child, with the proportion fluctuating weekly between 36.9 percent and 87.5 percent.
Children 8 years and younger were more likely to be a source of transmission than those 9 to 17 years old (7.6 percent versus 5.8 percent). During most of the epidemic, the proportion of transmission from children was negatively correlated with new community COVID-19 cases.
“More than 70 percent of transmissions in households with adults and children were from a pediatric index case, but this percentage fluctuated weekly,” the researchers said. “Once US schools reopened in 2020, children contributed more to household transmission estimates while they were in school, and less during summer and winter breaks, a pattern for 2 consecutive school years.”
The researchers said that pediatric Covid-19 transmission was negatively correlated with new community cases during most of the epidemic, which is consistent with a previous study.
“When the incidence of Covid-19 rises, adults in the community are at greater risk of infection; this may increase the likelihood that adults become the index case in household transmission and explain the negative correlation we observed.” , “said the researchers.
“Furthermore, when the COVID-19 outbreak subsides, the overall use of non-pharmacological interventions may decrease, which may increase the incidence of non-SARS-CoV-2 pathogens that may be more common in children. ”
The team concluded that children had an important role in the spread of SARS-CoV-2 and that in-person schooling also contributed to a substantial spread.