Restaurants, fast-food chains and hotels are the three places where people are most likely to catch coronavirus, scientists have warned.
Researchers analysed nearly a million businesses in eight US states during the crisis, including New York and California.
They said restaurants, fast-food chains and hotels were ‘super-spreader’ businesses because they are often densely packed, and people linger in close proximity for long periods of time.
It may explain why the US – where people are thought to eat out up to four times a week – has become the Covid-19 capital of the world.
New York and California are two of the worst-hit states in the US, suffering 367,000 and 97,000 infections, respectively. The densely populated states are also home to the highest number of restaurants.
According to the National Restaurant Association, California has by far the the most eateries at 87,225, followed by New York State, where there are 58,027 restaurants.
It comes as a total of 38 US states have now allowed restaurants to reopen for dine-in services of some kind, or have announced plans to do so.
In most states they have only been allowed to run at 25 to 50 per cent capacity and tables must be six feet apart.
New York and Philadelphia have been two of the worst-hit regions in the US during the pandemic (left), while California has had major outbreaks of its own (right)
In the state of New York, more than 23,00 people had died as of May 15. This include at least 765 nursing home deaths
In comparison to New York, the entire state of California, which acted early to shut down, had only 3,774 deaths as of May 25
Experts believe many clusters of Covid-19 infections can be blamed on so-called ‘super-spreading’ events.
In most cases, these coronavirus outbreaks can be traced back to a singular highly infectious person, known as a ‘super spreader’.
Around one in 10 people who get the virus transmit infections to far more people than the majority do.
As of May 25, more than 16,565 people died from coronavirus in New York City
There are a number of theories as to why they are more infectious – but no definite answer.
Some suggest the immune systems of super-spreaders are unable to suppress the virus.
Others say their immune systems may be so good they do not experience symptoms so they carry on life as normal and transmit it to others.
In the new study, researchers from the Beth Israel Deaconess Medical Center in Boston, Pennsylvania State University and the University of Pennsylvania analysed coronavirus transmission in 918,094 businesses in eight states.
They did this by breaking down Covid-19 cases by county between January 22 and May 22 and comparing the data with pre-pandemic consumer behavior surveys.
The academics drew on data from the 2018 American Community Survey from the United States Census Bureau, which quizzed Americans on their frequency of visits to businesses and the average duration of their stay.
In total there were 187 counties in eight states, including Massachusetts, Rhode Island, Connecticut, New Hampshire, Vermont, Maine, New York, and California.
They identified 156,307 individual businesses as super-spreaders out of a total of 918,094 establishments.
Of the super-spreader businesses, 116,605 were dine-in restaurants, 26,196 were limited service restaurants, such as delis, fast food chains and takeaways, and 13,432 were hotels and motels.
The scientists said that there was a direct link between Covid cases and the number of restaurants, fast-food shops and hotels.
They warned of a second wave of the epidemic and more deaths, if tough restrictions are not in place when these establishments reopen.
Writing in the study – which has not yet been published in a journal or scrutinised by other scientists – the researchers said: ‘Even though the public and states are ready to to reopen the economy, experts cautioned on resurgence of the virus and death tolls if we open our economy prematurely.
‘Given the empirical evidence on the potential impact of super-spreaders in the spread of Covid-19, it is crucial to evaluate which businesses, events, establishments, and industries should reopen first and which ones may have a higher risk of spreading the virus.
‘We find a positive association between the density of super-spreader businesses and Covid-19 cases.
‘Our results suggest an increase in super-spreader businesses by one percentage point results in a 5 per cent increase in Covid-19 cases, all else equal.’
The researchers also found people were much less likely to catch the virus in open-air establishments, such as beer gardens and outdoor eateries.
They said the risk was 18 times lower than somewhere that had a closed roof, due to a lack of fresh air.
It comes after separate research identified choir meetings, gym classes and business conferences as ‘super-spreading’ events.
Experts from the London School of Hygiene and Tropical Medicine found many outbreaks of Covid-19 infections can be blamed on so-called ‘super-spreading’ events.
Gyms lend themselves as the perfect place for the virus to spread, due to the setting and because there are many people (stock)
Choirs, gym classes and business conferences and other ‘superspreader events’ may be responsible for most coronavirus cases, scientists say (stock)
The Centre for Disease Control and Prevention reported a large outbreak that was the result of a choir rehearsal in Washington State. Some 52 people became sick as a result of one index case (pictured). A total of 61 people attended the rehearsal
One of the best examples of this, they said, is a choir rehearsal in Washington State where 87 per cent of the 61 singers ended up with the infection.
Scientists at London School of Hygiene and Tropical Medicine say around 80 per cent of Covid cases are caused by super-spreaders.
The researchers said the focus of controlling the epidemic should be to limit events where super-spreaders could wreak havoc.
Super-spreading is known to occur in care homes, hospitals and religious places – but the scientists say other unusual events can lead to clusters of cases.