FRIDAY, Oct. 30, 2020 (HealthDay News) -- COVID-19 can spread through a family like wildfire, frequently infecting other people in a household within days of someone carrying the coronavirus home with them, new research shows.
More than half of people in households with COVID-19 patients wound up contracting the virus themselves, usually within five days of the first patient developing symptoms, according to findings from the U.S. Centers for Disease Control and Prevention.
The study tracked 101 people initially diagnosed with COVID-19 in the cities of Nashville, Tenn., and Marshfield, Wis., between April and September, according to a report published Oct. 30 in the CDC's Morbidity and Mortality Weekly Report.
Those initial patients lived with a total 191 other people in their households, and researchers took specimens from the others in the house to track the infectiousness of the COVID-19 coronavirus.
Out of those 191 secondary household contacts, 102 tested positive for the coronavirus -- about 53%, the researchers said.
Three out of four (75%) of these secondary infections occurred within five days of the first person falling ill. During seven days of follow-up, two-thirds (67%) of infected household members reported symptoms of COVID-19.
"We observed that after a first household member became sick, several infections were rapidly detected in the household," lead researcher Dr. Carlos Grijalva, an associate professor of health policy at Vanderbilt University Medical Center in Nashville, said in a university news release. "Those infections occurred fast, whether the first sick household member was a child or an adult."
The age of the first patient didn't seem to make much difference in whether or how rapidly COVID-19 spread through a home, researchers found. Of the initial patients, 14 were age 17 and younger, 65 were between 19 and 40, and 22 were 50 or older.
"Understanding that children may also serve as a vector within a household was an important finding to emerge from this CDC report," said Dr. Robert Glatter, an emergency physician with Lenox Hill Hospital in New York City.
About 70% of the initial COVID-19 patients reported spending more than four hours in the same room with one or more household members the day before they fell ill, and 40% said they spent as much time in the same room with others even after developing symptoms.
Similarly, 40% of the first patients said they slept in the same room with at least one other person before they developed COVID-19, and 30% did so after they fell ill.
The data highlight the risk of asymptomatic transmission of COVID-19, the researchers said. Fewer than half of household members with confirmed infections reported symptoms at the time they tested positive, and about a third reported no symptoms during seven days of follow-up.
"These findings suggest that transmission of SARS-CoV-2 within households is high, occurs quickly and can originate from both children and adults," the researchers concluded.
"Recognizing the home as a potential source of spread is vital to controlling the pandemic, as cases, hospitalizations and deaths are significantly increasing in the U.S. in the past few weeks," said Glatter, who wasn't part of the study.
"To prevent transmission, it's vital to stress the importance of self-isolating at home and self-quarantining of any potential household contacts," Glatter continued. "Ideally, this should occur with the use of a separate bedroom and bathroom if possible."
Rapid antigen tests could help families keep track of transmission following someone coming down with COVID-19 in their home, if they become widely available, he said.
"Beyond this, all household members must wear a mask in shared spaces within any home setting. These measures can reduce the potential for household transmission," Glatter concluded.
The U.S. Centers for Disease Control and Prevention have more about COVID-19.
SOURCES: Morbidity and Mortality Weekly Report, Oct. 30, 2020; Robert Glatter, MD, emergency physician, Lenox Hill Hospital, New York City