A study that compared 154 “case-patients,” who tested positive for COVID-19, to a control group of 160 participants from health care facilities who were symptomatic but tested negative, showed that 70% of the case-patients were contaminated with the virus and fell ill despite “always” wearing a mask, according to the September 11 Centers for Disease Control (CDC) Morbidity and Weekly Mortality Report.
The study, conducted at 11 outpatient health care facilities* in California, Colorado, Maryland, Massachusetts, Minnesota, North Carolina, Ohio, Tennessee, Utah, and Washington last July. CDC personnel administered structured interviews in English or five other languages by telephone and entered data into REDCap software.
According to the report, “Participants with and without COVID-19 reported generally similar community exposures, with the exception of going to locations with on-site eating and drinking options. Adults with confirmed COVID-19 (case-patients) were approximately twice as likely as were control-participants to have reported dining at a restaurant in the 14 days before becoming ill. In addition to dining at a restaurant, case-patients were more likely to report going to a bar/coffee shop, but only when the analysis was restricted to participants without close contact with persons with known COVID-19 before illness onset.
Since the pandemic began, reports of exposures in restaurants have been linked to air circulation. Direction, ventilation, and intensity of airflow might affect virus transmission, even if social distancing measures and mask use are implemented according to current guidance. Masks cannot be effectively worn while eating and drinking, whereas shopping and numerous other indoor activities do not preclude mask use. Among adults with COVID-19, 42% reported close contact with a person with COVID-19, similar to what has been reported previously (4). Most close contact exposures were to family members, consistent with household transmission of SARS-CoV-2 (8). Fewer (14%) persons who received a negative SARS-CoV-2 test result reported close contact with a person with known COVID-19.
To help slow the spread of SARS-CoV-2, precautions should be implemented to stay home once exposed to someone with COVID-19, in often, wear masks, and social distance. If a family member or other close contact is ill, additional prevention measures can be taken to reduce transmission, such as cleaning and disinfecting the home, reducing shared meals and items, wearing gloves, and wearing masks, for those with and without known COVID-19, the study authors urged.
Report Limitations Explained
The findings in the report are subject to at least five limitations, the authors noted.
“First, the sample included 314 symptomatic patients who actively sought testing during July 1–29, 2020 at 11 health care facilities. Symptomatic adults with negative SARS-CoV-2 test results might have been infected with other respiratory viruses and had similar exposures to persons with cases of such illnesses.
Second, the survey question assessing dining at a restaurant did not distinguish between indoor and outdoor options. In addition, the question about going to a bar or coffee shop did not distinguish between the venues or service delivery methods, which might represent different exposures. The subjects may have concurrently participated in activities where possible exposures could have taken place, that were not included in the analysis or measured in the survey.
Third, adults in the study were from one of 11 participating health care facilities and might not be representative of the United States population.
Fourth, participants were aware of their SARS-CoV-2 test results, which could have influenced their responses to questions about community exposures and close contacts.
Finally, case or control status might be subject to misclassification because of imperfect sensitivity or specificity of PCR-based testing.”
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