Majority of patients don’t know source of infection

New CDC survey finds that 54% of patients are unaware of specific contact with infected person

More than half of people with COVID-19 have no idea how or where they got infected — underscoring the need for social distancing, more widespread use of masks and better contact tracing, especially at work.

That is the conclusion of a new survey by the Centers for Disease Control, released Tuesday, of 350 patients in nine states treated at 11 academic medical centers, including Stanford University and UCLA.

It found that 54% of patients were unaware of recent close contact with a COVID-19 patient.

“Simply avoiding people who have known coronavirus is not sufficient to stop the spread of the virus because less than half of the patients had a known close contact,” said Dr. Jennifer Wilson, clinical assistant professor of emergency medicine at Stanford University Medical Center.

“They got it from someone who they didn’t know or didn’t know well,” she said. “That reinforces the fact that when we go out into the community, we need to assume that we can get it from anyone at any time.”

Of patients who knew the source of their illness, 45% said they likely were infected by close contact with a sick family member, 34% by a work colleague and 10% by a friend. Others said they were exposed in a health care setting, assisted living facility, correctional facility or by a neighbor or client at work.

Until now, reports about sources of exposure to the COVID-19 virus have been focused on so-called congregate settings, such as meat and poultry processing plants and longterm care facilities. And these reports focused primarily on patients who were so sick that they required hospitalization.

This new survey, conducted by phone, is seen as a much more representative snapshot of the individual behaviors and demographic characteristics of patients in the general population, both inpatient and outpatient.

About two-thirds — 64% — of these patients were employed. Of these, only 17% worked remotely, through telework.

“Very few of the people who were infected were able to telecommute,” said Stanford’s Wilson. “This really underscores the importance of workplace safety and about thinking more broadly about social and public health measures to help protect essential workers.

“We need to keep physical distancing and keep wearing a mask to decrease the risk of community spread,” Wilson added.

The new findings come at a time of surging infections in many states, including California, as counties begin reopening and testing is expanded.

The CDC report is based on

telephone surveys from April 15 to May 24 of a sample of patients who were either hospitalized or received outpatient care and tested positive March 31 through May 10. They were asked about exposure — defined as being within 6 feet of someone with a COVID-19 diagnosis

— during the two weeks before their positive test result or illness.

The Stanford-specific data, obtained from patients who received either inpatient or outpatient testing at the hospital, was not available.

The average age of outpatients was 42, and the average age of inpatients was 54. Inpatients were less likely to be white and more likely to have an annual household income of

less than $25,000. Inpatients also had more underlying chronic conditions, such as cardiovascular disease, chronic respiratory disease or diabetes.

About one-third of sick people seen as outpatients reported that their health still had not returned to normal two to three weeks after testing positive.

Patients described a broader range of symptoms than previously de

scribed, including not just shortness of breath, fever and cough but also chest pain, abdominal pain, nausea, vomiting, diarrhea, confusion, fatigue and a loss of smell or taste.

“The wide range of

symptoms reported, and the lack of known COVID-19 contact in 54% of patients,” the report concluded, “underscores the need for isolation of infected persons, contact tracing and testing during

ongoing community transmission, and prevention measures including social distancing and use of cloth face coverings.”