[Analytics] Why safer social distance differs around the world

Social distancing signs at Ikea in Sydney. Picture: News.com.au / Benedict Brook. Sketched by the Pan Pacific Agency.

If you go to the supermarket this week, you’ll likely end up queuing behind stickers on the floor imploring you to maintain a distance of 1.5 metres. Across the ditch in New Zealand shoppers there are urged to stand two metres apart, as they are in the UK. In the US that same safe distance is 1.8 metres. Yet in Singapore, it’s just 1 metre. Benedict Brook specially for the News.com.au.

Research released earlier this month said we should be even more distant that 1.5m from one another, particularly when exercising, perhaps as much as five or 10 metres.

Given we’re probably going to have to keep social distancing for some time, how apart should we be? Singapore’s single metre, Australia’s still snug 1.5 metres, New Zealand’s more generous two metres or far more?


Whatever the distance, the aim remains the same. To keep your face a suitable distance from the respiratory droplets that someone with COVID-19 might unintentionally expel in your direction. If those teeny, tiny but virus laden droplets find their way into your mouth, eyes or nose, you could become infected.

But droplets can only be expelled so far before they lose momentum and begin to drift towards the ground.

The problem, said Philip Russo from Monash University’s School of Nursing and Midwifery, was that exactly how far they are expelled is all a bit of a guessing game.

“There is a lack of good evidence to know for sure how far infectious droplets travel, and what is a ‘safe’ distance.

“Research is often laboratory based and doesn’t automatically translate to real-life situations. Then there are the variables about the number of infectious particles; their airborne survival; the humidity; and the speed of expulsion,” Prof Russo said.

The current social distancing recommendations are based on how the flu is spread. COVID-19 is not the flu, but it has enough in common with it that it’s a good place to start.

Prof Russo cautioned, however, that because coronavirus is new there is a “lack of scientific rigour” and so a discrepancy between different health bodies’ advice on physical distancing.

The World Health Organisation has had a longstanding recommendation that people should put at least one metre between them and someone with the symptoms of influenza.

Indeed guidelines from Australia’s National Health and Medical Research Council regarding droplet transmission from infected people states “it is limited by the force of expulsion and gravity and is usually no more than one metre”.

However, the UK’s National Health Service – along with some other health bodies – has doubled this distance to two metres.

Australia, as well as countries like Germany, has landed between the WHO’s 1m guidance and the NHS’ two.

“Given COVID-19 is transmitted through droplets, 1.5m is actually greater than that recommendation, so 1.5m could be viewed as extra cautious,” Dr Russo told news.com.au.


Just to mix it up a bit, the US Centres for Disease Control (CDC) has given a guideline of 1.8 metres.

This seemingly arbitrary number is likely due to the fact the US, almost uniquely worldwide, still uses imperial measurements. Advising people to stand 2m apart while waiting to get into supermarkets from Washington DC to Washington state might lead to some scratching of heads. But almost everyone there can gauge a distance of six foot, that’s around 1.8 metres.

But there is also some science behind that number as well. A study from 2013 found the risk of healthcare workers contracting flu from an infectious patient declined hugely once they were more than 1.8 metres distant.

However, this was in a high-risk situation with prolonged care and lot of coughing and spluttering. That hopefully won’t be the case in the cereal aisle at Woolies.

Here in Australia, 1.5 metres neatly translates into about the length of a shopping trolley which is again easy to visualise. Or actually hold.

Earlier this month, Melbourne Royal Children’s Hospital intensive care doctor Warwick Butt said social distancing guidelines were based on science – but only up to a point.

“All of those distances are made up from bacterial pneumonia and some very old cough studies,” he told the Herald Sun.

“I think most of them went less than half a metre, and people just said, ‘make it a metre and a half for safety!’ I don’t think there’s any signs as to whether it should be 1m, 1.5m or 2m.”

Bond University professors Tammy Hoffman and Paul Glasziou have highlighted how much of our current practices to fend off coronavirus are essentially best guesses.

“Debates still rage over basic questions such as whether the public should use face masks; whether we should stand one, two or four metres apart; and whether we should wash our hands with soap or sanitiser.”


Is even two metres enough though?

Dutch researchers have said when people are exercising, you should leave a gap of five metres behind runners or 20m for cyclists.

A somewhat alarming video simulation showed runners could expel droplets that then hung in the air for enough time for another jogger to run into the potentially infectious cloud.

Running side-by-side, while keeping apart, might be more advisable, the firm suggested.

But Emmanuel Stamatakis, a professor of physical activity at the University of Sydney has pointed out the paper has yet to be peer reviewed and was based on computer simulations rather than real world research.

“The quality of the simulation could be anything between flawed and reasonably realistic.

He said maintaining a distance of up to 20m behind a cyclist would make it “almost impossible” to exercise in crowded cities and could deter people from going out at all.

Although he added popular running tracks should be avoided when busy.

“Stick to official advice and do not rush to make any new lifestyle decisions.”


Prof Russo warned not to get too hung up about the differing advice on minimum physical distances.

“Right now, avoiding close contact with others is important, and keeping 1.5m away from each other is not an exact science … nor is it absolutely guaranteed to prevent spread. But that approximate distance is better than no distance,” he wrote in a recent piece for The Conversation.

“We need to be practical. The greater the distance the less likely of droplet contamination. But you can’t have a conversation with someone who is a few metres away. Guidelines fail if they can’t be implemented. So 1.5m is practical and easily implemented.

“It’s about two arms lengths, but don’t stress about it. A little bit less is OK, a little bit more is good.”

And, remember, hand washing and staying at home if you feel ill are just as vital as keeping your distance, whatever distance that may be.

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