Spending time in a bar or restaurant increases the risk of catching Covid-19, French researchers said on Thursday, while guests at dinner also play a key role in the transfer.
The latest study adds evidence that socializing and eating out is much more dangerous than other activities such as using public transportation or shopping.
Europe and the United States in particular are struggling with rising rates of Covid-19 infection and the start of a holiday season that is usually marked by parties and family gatherings.
Researchers from the French Institute Pasteur tried to find out what factors – such as occupations, modes of transport, places visited – differentiated participants who had contracted the virus from people who had not.
“We saw an increased risk associated with visiting bars and restaurants,” said lead author Arnaud Fontanet, an epidemiologist and member of the government’s scientific council.
The study, called ComCor, has not been reviewed by colleagues but has informed France’s virus response.
It was carried out in October and November, during a first period with a curfew and then even stricter restrictions which saw that most facilities were closed in whole or in part.
Fontanet told AFP that because bars and restaurants do not operate as usual, it was difficult to assess their exact role in the transfer and acknowledged that it was a “sensitive” measure to close these companies.
French cafes and restaurants have been closed even after nationwide restrictions were eased earlier this week.
ComCor researchers interviewed 3,400 people infected with Covid-19 and 1,700 others who did not have the virus.
They found that frequent restaurants, bars or gyms were associated with an increased risk of infection, while not using public transport and visiting shops.
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Health authorities around the world have advised people to avoid cramped indoor spaces as researchers increasingly agree that the new coronavirus can travel in fine clouds of particles called aerosols that can accumulate in poorly ventilated rooms.
A September study by the US Centers for Disease Control and Prevention found that adults with positive coronavirus outcomes were about twice as likely to report eating at a restaurant in the previous two weeks as those with adverse outcomes.
In November, a study in the journal Nature found that restaurants, gyms and cafes account for most Covid-19 infections in the United States.
Using mobile phone data from 98 million people, researchers found that about 10 percent of the arenas accounted for more than 80 percent of the cases.
ComCor research also attempted to find different infection conditions, with studies of 25,600 infected individuals using health insurance data.
It showed that “meals play a central role in these pollutants”, as people sat close to each other without masks.
“Private meetings – families, friends – are the main source of infection,” says Fontanet.
“If people have friendly dinners at home rather than going to a restaurant, it makes no difference.”
The researchers stressed the importance of organizing such gatherings in the “safest way” to protect vulnerable people during the holidays.