November 3, 2020 -- A CDC report says the coronavirus spreads quickly among people living together -- so quickly that you should start wearing a facial covering inside shared spaces as soon as you think you or someone in your household is infected.

The CDC’s Morbidity and Mortality Weekly Report says more than 100 households in Nashville and Marshfield, WI, were studied from April to September to determine the rate of COVID transmission within a household.

Fifty-three percent of people living with somebody who tested positive ended up becoming infected themselves within a week, with 75% of the secondary infections confirmed within 5 days or less, the CDC said.

“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,” the study said

“Isolation should begin before seeking testing and before test results become available because delaying isolation until confirmation of infection could miss an opportunity to reduce transmission to others. Concurrently, all household members, including the index patient, should start wearing a mask in the home, particularly in shared spaces where appropriate distancing is not possible.”

While most health authorities now recommend face masks in public places -- especially while inside -- the wearing of masks inside a person’s own residence is a relatively new wrinkle.

Sixty-nine percent of sick, or “index,” patients reported spending 4 hours or more in the same room with another household member the day before they became ill. Forty percent of the index patients said they slept with another household member before they became sick and 30% did after they became sick.

Testing was self-administered. Ages of test participants ranged from under 12 to above 50.

The new CDC study confirms what infectious disease experts have said since the early days of the pandemic: The virus is often spread through close personal contact and that people may spread the virus before they show any symptoms.

“These findings suggest that transmission of SARS-CoV-2 within households is high, occurs quickly, and can originate from both children and adults,” the CDC said of the new study. “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.”

The CDC noted that it’s possible study participants became infected outside the household or that the second person to test positive for coronavirus was already infected when the index member’s infection was confirmed.

WebMD Health News Brief


CDC. “Transmission of SARS-COV-2 Infections in Households — Tennessee and Wisconsin, April–September 2020”

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