Some states have opened their restaurants, despite warnings from the Centers for Disease Control and Prevention (CDC), claiming that open-air dining has barely proved sustaining. In 2015, food and drink sales in the U.S. restaurant industry reached $745.61 billion with 19 million people having visited a full-service restaurant and over 49 million people having visited a quick service restaurant in 2016. Most restaurants are desperate to host diners indoors again, especially with cold weather looming.

Previously, there was no evidence to suggest that coronavirus disease 2019 ( COVID-19) was spread by handling or eating food. But that has changed with researchers’ claim that community and close contact exposures continue to fuel the spread of the virus.

The CDC now suggests that dining out increases risk of contracting coronavirus more than other activities, citing the fact that masks are not used while people are eating and drinking. In fact, a new CDC study found that people who tested positive for the coronavirus were twice as likely to have eaten at a restaurant beforehand.

The researchers collected data during the month of July across 10 states from 314 adults with coronavirus symptoms. The participants lived in states with differing reopening guidelines, including California, Colorado, Maryland, Massachusetts, Minnesota, North Carolina, Ohio, Tennessee, Utah, and Washington. About half of them (154) tested positive for the virus.

Participants were asked about possible community exposure in the two weeks leading up to their test, including whether they recently dined at a restaurant, worked at an office, went shopping, went to the gym, attended a church gathering, or used public transportation frequently. They also had to rate how well they followed social-distancing measures at the location of each activity.

Researchers found that 42% of those who tested positive said they had close contact with at least one person with COVID-19, most of whom (51%) were family members, two weeks before their test. A lower proportion (14%) of the participants who tested negative reported having close contact with a person with known COVID-19 in the two-week period before their test.

About 71% of the those who tested positive, and 74% of those who tested negative, said they always wore a face covering while in public in the two weeks before their test, although the type of mask was not specified. In addition to dining at a restaurant, participants were more likely to have gone to a bar or coffee shop but only when the analysis was restricted to participants without close contact with persons with known COVID-19 before illness onset.

Experts have previously warned that air circulation in indoor spaces and gatherings, such as restaurants, could affect virus transmission. However, participants did not have to specify whether they ate indoors or outdoors while dining out, suggesting that more research is needed to establish whether the findings would be similar to a larger group of people.

The CDC guidelines currently recommend that takeout, drive-thru facilities, or delivery services pose the lowest risk of contracting the coronavirus from a restaurant, while the highest risk would be offering indoor and outdoor dining where tables are neither reduced nor spaced at least 6 feet apart.