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Social distancing: The science behind the two-metre rule

Ministers are reported to be considering whether to relax the two-metre rule for social distancing in workplaces. It could make it easier for people to get back to jobs where it is not always feasible to stay apart. But a key question is whether that would be safe, given how little is known about how far the virus can spread.
A new report by the government's scientific advisers is due to be released shortly assessing latest research into the risks.
What does science say about the rule?
There is a wide variety of recommendations in different countries, but a simple guide is that the closer you are to someone who is infected, the greater the risk. The World Health Organization says that a distance of one metre is safe, while others suggest 1.5m or 1.8m with the UK opting for two metres. Also the longer you spend in close proximity with an infected person, the more your chances of catching the virus go up.
One leading scientist says that timing can really make a difference. "Spending two seconds one metre apart is as dangerous as spending one minute two metres apart," he says.
Where does the two-metre rule come from?
Surprisingly, it can be traced back to research in the 1930s. Back then scientists established that droplets of liquid released by coughs or sneezes will either evaporate quickly in the air or be dragged by gravity down to the ground. And the majority of those droplets, they reckoned, would land within one to two metres. That is why it is said the greatest risks come from having the virus coughed at you from close range or from touching a surface - and then your face - that someone coughed onto.
Some researchers are now concerned that the coronavirus is not just carried in droplets. They worry that it can also be transported through the air in tiny particles called aerosols. If that is the case, then the flow of wind from someone's breath could carry the virus over longer distances.
Could wearing face masks help?
Amid the uncertainty, many governments are urging - or ordering - their citizens to cover their faces. In Spain, anyone using public transport from Monday will have to wear a mask, and the same applies in Germany. The logic is that where keeping apart is not realistic - up to whatever distance is recommended - then even a homemade covering can limit how much virus is released from an infected person's mouth or nose. The Scottish government is among those to recommend that in confined spaces, a non-medical mask should be worn. The UK government is still considering what to advise the British public as a whole.
Health professionals have long worried that medical and care staff might lose out if supplies are snapped up and that masks would give people a false sense of security leading them to give up other measures like social distancing.
Prime Minister Boris Johnson has suggested that masks might help slow the spread of the disease.

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Social distancing: The science behind the two-metre rule - by Vanessa Angotti - 05-06-2020, 05:38 AM

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