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Infectious Diseases

06 June 2020

2m of physical distancing best, but even 1m should help

A Canadian study found that face masks, eye protection and keeping at least one metre away from people give you the best chance of avoiding infection.

  • The more 'layers of protection' you have, the better your chances of avoiding infection
  • No precautions are 100% foolproof
  • Masks need to have more than one layer of fabric to be effective

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"Physical distancing" is the watchword for keeping the new coronavirus at bay, but how far apart is enough? Researchers say they may have an answer.

While most public health officials recommend you put 6ft (2m) between yourself and others, a new review of 172 studies from 16 countries concluded that keeping 3ft (1m) apart might also protect you to some degree.

And while face masks and eye protection might add even more layers of protection, these precautions aren't 100% foolproof, the researchers added.

Still, the Canadian study found that face masks, eye protection and keeping at least 3ft (1m) away from people give you the best chance of avoiding infection.

Clear advice on protective measures

"Our findings are the first to synthesise all direct information on Covid-19, SARS and MERS, and provide the currently best available evidence on the optimum use of these common and simple interventions to help 'flatten the curve' and inform pandemic response efforts in the community," said study co-author Dr Holger Schünemann, a professor at McMaster University in Hamilton, Ontario.

"Governments and the public health community can use our results to give clear advice for community settings and healthcare workers on these protective measures to reduce infection risk," Schünemann added.

He and his colleagues found that keeping 3ft or more apart from others was linked with a lower risk of infection, compared with less than 3ft of distancing. The risk of infection by keeping a distance of 3ft or more away from the infected individual was 3% versus 13% when the distance was less than 3ft.

The report was published on 1 June in The Lancet medical journal.

When it comes to face masks, N95 and other respirator-type masks might confer greater protection from Covid-19 infection for health care workers than simple surgical masks. For the general public, face masks are also associated with protection, even in non-health care settings, the researchers said.

"With respirators such as N95s, surgical masks, and eye protection in short supply, and desperately needed by healthcare workers on the front lines of treating Covid-19 patients, increasing and repurposing of manufacturing capacity is urgently needed to overcome global shortages," said study co-author Dr Derek Chu, an assistant professor at McMaster University.

'An important milestone'

"We also believe that solutions should be found for making face masks available to the general public," Chu said in a journal news release. "However, people must be clear that wearing a mask is not an alternative to physical distancing, eye protection or basic measures such as hand hygiene, but might add an extra layer of protection."

In an accompanying commentary, Raina MacIntyre, head of the Biosecurity Program at the Kirby Institute at the University of New South Wales in Australia, describes the study as "an important milestone".

"For health care workers on Covid-19 wards, a respirator should be the minimum standard of care," MacIntyre said. "This study by Chu and colleagues should prompt a review of all guidelines that recommend a medical mask for health workers caring for Covid-19 patients."

The study also offers important guidance on the homemade masks many Americans are wearing, MacIntyre added.

Since the researchers report that respirators and multilayer masks are more protective than single-layer masks, homemade cloth masks should have "water-resistant fabric, multiple layers and good facial fit", MacIntyre added.

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