Researchers at the US Centers for Diseases Control and Prevention (CDC) have said that restaurants seem to play a pivotal role in the spread of COVID-19, the infection caused by the new coronavirus called SARS-CoV-2.

CDC’s Dr. Kiva Fisher and colleagues wrote, “Masks cannot be effectively worn while eating and drinking, whereas shopping and numerous other indoor activities do not preclude mask use.”

Dr. Fisher is the Epidemic Intelligence Service Officer at the CDC.

The researchers published their findings last week in the Morbidity and Mortality Weekly Report (MMWR).

Public health officials have recommended practicing social distancing and wearing masks to prevent the spread of the virus but knowing exactly where people have been catching the virus could help hone those recommendations, according to the researchers.

The team also found that most research into the ways people have caught the virus has not included control groups. To address that, they compared 154 adults with COVID-19 symptoms and had tested positive for the virus with 160 adults who had similar symptoms but tested negative.

The researchers asked the participants about wearing a facemask and potential community exposure activities, including attending gatherings with less or more than 10 people in a home; shopping; dining at a restaurant; going to an office, salon, gym, bar, coffee shop, or church/religious gathering; or using public transportation.

The participants were asked to respond using a five-point scale, ranging from “never” to “always.”

Of those who tested positive for COVID-19, 42% said having close contact with someone with COVID-19 compared to 14% of those who tested negative. More than 51% of the participants caught the infection through family members.

The participants who tested positive were 2.4 times more likely to have dined at a restaurant in the 2 weeks before falling sick. And those who tested positive were four times as likely to have gone to a bar/coffee bar.

Over 70% of the participants who were tested positive said they always used facemasks or other types of coverings in public.

The team noted that apart from the difficulty of wearing facemask while dining, some participants reported poor ventilation systems of restaurants.

However, there were a few limitations to the study. For instance, many of the participants they contacted refused to participate. Also, there could be differences in participation among those who tested positive and negative.

The researchers conclude, “Implementing safe practices to reduce exposures to SARS-CoV-2 during on-site eating and drinking should be considered to protect customers, employees, and communities and slow the spread of COVID-19.” The article originally appeared on Medscape Medical News.