Coronavirus: Could social distancing of less than two metres work?
Two people on a bench
The government will make proposals this week to safely reduce the 2 million rule on social distancing in England.
"Weakening" could reduce the distance so that people can get closer without a higher risk of transmission, Health Minister Matt Hancock H told the BBC.
The review of the 2-meter rule on social distancing was first announced on June 14 by British Prime Minister Boris Johnson.
The government was under pressure from MPs and the hotel industry to enable people to be closer together and help businesses after their reopening.
However, the government's scientific advisors say that a distance of 1 m carries 10 times the risk of a distance of 2 m.
What does science say?
The simple answer is: the closer you are to someone who is infected, the greater the risk of contracting the virus.
The World Health Organization recommends keeping a distance of at least 1 m.
Some countries have adopted these guidelines, often because they also insist that people wear masks.
Others, including Britain, have gone further:
1m distance rule - China, Denmark, France, Hong Kong, Lithuania, Singapore
1.4 m - South Korea
1.5 m - Australia, Belgium, Germany, Greece, Italy, Netherlands, Portugal
1.8 m - USA
2m - Canada, Spain, Great Britain
What is the latest research?
In a study published in the medical journal The Lancet, scientists investigated the spread of the coronavirus.
They concluded that a minimum distance of 1 m from other people could be the best way to limit the risk of infection.
The risk of infection is estimated at 13% within 1 m, but only 3% beyond this distance.
And the study says that the risk is halved for every additional meter distance up to 3 m.
Graphic of social distance rules around the world
Where does the distance rule come from?
It can be traced back to research in the 1930s.
Scientists found that droplets of liquid released by coughing or sneezing evaporate quickly in the air or fall to the ground.
Most of these droplets would land within 1-2 meters.
For this reason, it is said that the greatest risks are that the virus will be coughed at close range or that you will touch a surface that someone has coughed on and then touch your face.
Two women on a bench by the sea
Can the virus spread any other way?
Proximity and surface contact are considered to be the main means of transmission.
However, some researchers fear that the coronavirus can also be transported through the air in tiny particles, known as aerosols.
If so, the wind from a person's breath can transmit the virus over long distances.
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Prof. Lydia Bourouiba of the Massachusetts Institute of Technology (MIT) used high-speed cameras to capture a cough that projects miniature spots up to 6 m.
A study conducted in Chinese hospitals, in which traces of coronavirus were found in Covid-19 and intensive care units, showed that 4 m is a better safety distance.
However, the US Centers for Disease Control say that the role of aerosols in the spread of the virus is "currently uncertain".
And what is not yet known is whether a virus that spreads more than 2 m can still be infectious.
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It's not just about distance
Timing is key too. The longer you are in the immediate vicinity of an infected person, the greater the risk.
Scientists who advise the UK government say spending six seconds at 1 m from someone is equivalent to 1 minute at 2 m.
Exposing to someone who coughs is riskier. Being 2 meters from a cough carries the same risk as someone who speaks to you at the same distance for 30 minutes.
The quality of ventilation is also important
A crowded, stuffy room inevitably increases the risk of infection.
The direction of the air flow is also critical - whether a draft or a fan behind an infected person is pushing a virus that they are breathing out.
And a good fresh air supply can make the difference.
In a restaurant in China where nine people were infected with the virus, the wall-mounted air conditioners were accused of circulating rather than freshening up the air.
Japanese researchers examined 110 cases of Covid-19 and found that indoor infection was almost 19 times more likely than outside.
What else makes a difference?
Scientists who advise the UK government say that every job or building should assess the risks.
And they say that where 2 m of social distance is impossible, people should only be closer for a short time.
Plastic screens are suggested along with the move to shift work patterns to minimize the number at a given time.
It is also judged that seating is arranged so that people are not face to face.
And in a growing number of countries, including all parts of the UK, people are encouraged to wear facewear and "closed spaces where social distance is not always possible" in public transport.
People social distancing on a tube platform
Why don't we have clear answers?
It's only been a few months since the corona virus appeared, and in that short period of time, scientists have learned a lot about it.
However, we still don't know how much virus can be released by infected people and how much someone needs to get to get the disease.
Until that is clear, the advice is that the risks are real - and that the distance guidelines can only be relaxed if the number of people infected drops dramatically.
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