Oct. 30 (UPI) -- Children age 12 years and younger infected with COVID-19 pass the virus to other members of their households more than half of the time, according to data released Friday by the U.S. Centers for Disease Control and Prevention.
Teens aged 12 to 17 years infected others in their households nearly 40% of the time, the data showed.
The findings are based on an analysis of the household contacts of 101 "index cases" of COVID-19 in Tennessee and Wisconsin between April and September, the agency said.
The index cases -- or people infected with the virus -- in the study had a total of 191 household contacts -- people living in the same home.
Among household contacts of the index cases included, 102, or 53 percent, were found to be infected with the virus -- 75% of them within five days of exposure, the CDC said.
"Transmission of [COVID-19] among household members was common, and secondary infection rates were higher than have been previously reported," researchers wrote.
"Because prompt isolation of persons with COVID-19 can reduce household transmission, persons who suspect that they might have COVID-19 should isolate, stay at home, and use a separate bedroom and bathroom if feasible," they said.
Forty percent of household members with confirmed infections reported symptoms at the time the disease was first detected in testing, the CDC said.
Research on the role of children in the spread of COVID-19 has been inconclusive, although the issue has drawn great attention since summer and fall as districts across the country considered reopening schools in the midst of the pandemic.
Just two of 34 households with multiple lab-confirmed COVID-19 infections in Chicago reported cases of child-to-child transmission, and only two others had instances of child-to-adult transmission, a study published in June in the Journal of the Pediatric Infectious Diseases Society found.
However, research in Europe has documented child-to-child transmission in schools in Denmark, Germany and Sweden, each of which handled school closures differently as the pandemic spread.
The new CDC data is part of an ongoing study tracking the spread of COVID-19 in two communities -- Nashville and Marshfield, Wis. -- the agency said.
Fourteen of the index patients included in the analysis were children and teens age 18 years and younger, and 20 of the 102 cases of household transmission were attributed to them, the data showed.
Of the index patients, 69% reported spending more than four hours in the same room with one or more household members the day before and 40% did so the day after illness onset, according to the CDC.
In addition, 40% of index patients reported sleeping in the same room with one or more household members before illness onset and 30% did so after symptoms first appeared, the agency said.
"These findings suggest that transmission of [COVID-19] within households is high, occurs quickly, and can originate from both children and adults," the agency researchers wrote.
"Prompt adoption of disease control measures, including self-isolating at home, appropriate self-quarantine of household contacts, and all household members wearing a mask in shared spaces, can reduce the probability of household transmission," they said.