The Morbidity and Mortality Weekly Report published by the US Centers for Disease Control and Prevention (CDC) on September 11 features an investigation of adults aged 18 years and above who were tested for SARS-CoV-2 at an outpatient testing or healthcare centre in the US from July 1 to July 29.
The study found that adults with positive SARS-CoV-2 were twice likely to have reported dining at a restaurant than those with negative SARS-CoV-2 results. The results highlight the differences in community and close contact exposures between adults who tested positive for COVID-19 and those who tested negative, and has implications for risk factors that may need to be considered as countries across the world are resuming activities.
“Exposures and activities where mask use and social distancing are difficult to maintain, including going to locations that offer on-site eating and drinking, might be important risk factors for SARS-CoV-2 infection,” the investigation mentions.
What does the analysis tell us?
In the investigation, participants with and without COVID-19 reported largely similar community exposures, with the exception of those who engaged in on-site eating. Essentially, the investigation shows that adults with COVID-19 were twice likely than control-participants (symptomatic adults with negative SARS-CoV-2 results) to have reported dining at a restaurant 14 days prior to becoming ill.
Further, approximately half of the participants reported shopping or visiting people inside their homes (in groups of 10 or less) on at least one day during the 14 days before symptom onset.
Among the adults who had COVID-19, over 49 per cent reported having close contact with a COVID-19 positive person. Most of the close contact exposures were with family members. On the other hand, among those who tested negative for COVID-19, about 14 per cent reported close contact with a COVID-19 positive person.
So does dining out increase the chances of contracting infection?
The investigation notes that reports of exposures in restaurants have been associated with air circulation since the direction, ventilation and intensity of airflow can impact virus transmission, despite adhering to social distancing measures and mask usage. Further, wearing masks in restaurants is not always possible, which might increase the exposure as compared to activities such as shopping or visiting someone’s house, which while indoor do not require individuals to take off their masks.
One of the earliest studies to prove this was a research from China that came out in April and talked about an incident in a restaurant in Guangzhou, China, in which one coronavirus-positive diner passed on the infection to nine more people dining there, but not to others. In this study, the researchers concluded that droplet transmission by air-conditioned ventilation.
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What are the limitations of the investigation?
The study did not distinguish between outdoor and indoor dining in and included only 314 symptomatic individuals who sought testing at 11 centres in the US. Therefore, the results may not be representative of the general population. Participants were also aware of their test results, which might have influenced their responses to questions regarding community exposures and close contacts.
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