CDC: COVID-19 patients infect half the people in their homes

Adults only slightly more likely than children to spread the virus

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If you have COVID-19 symptoms, a new CDC report states, you should isolate yourself as soon as possible, even from your family.

That’s because people with COVID-19, the disease caused by the coronavirus, infect about half the people in their household, the Centers for Disease Control and Prevention in Atlanta determined.

The CDC’s study followed index patients — the first person in a household with a lab-confirmed positive test result — in Nashville, Tennessee, and Marshfield, Wisconsin, from April to September.

The 101 index patients and the 191 members of their households were trained to keep a symptom diary and collect specimens, either through nasal swabs alone or swabs and saliva samples, for 14 days.

According to the study, no one in the households reported having symptoms at the onset of the index patient’s symptoms. By the end of the 14 days, however, 102 of them tested positive. That’s a secondary infection rate of 53%.

“Approximately 75% of secondary infections were identified within 5 days of the index patient’s illness onset, and substantial transmission occurred whether the index patient was an adult or a child,” the CDC wrote.

Secondary infection rates were high across all racial and ethnic groups, and substantial transmission occurred whether the index patient was an adult or a child.

“Because household transmission of SARS-CoV-2 is common and can occur rapidly after the index patient’s illness onset, persons should self-isolate immediately at the onset of COVID-like symptoms, at the time of testing as a result of a high risk exposure, or at the time of a positive test result, whichever comes first,” the scientists wrote.

Everyone in the home should also wear a mask, especially in shared spaces where distancing isn’t possible.

Isolation of people who test positive for COVID-19 can reduce household transmission, the CDC said, and index patients also should stay home, and use a separate bedroom and bathroom if possible.

“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,” the CDC said.

One important finding, the scientists pointed out, is that more than half of the index patients reported having no symptoms when their infection was first detected, and many reported no symptoms during the first seven days of follow-up.