The strict social distancing rule of standing one metre from others during the coronavirus pandemic is outdated, claim UK scientists.
That’s because it doesn’t account for the ways respiratory droplets can travel in different environments.
The researchers, from the University of Oxford, said when people cough and shout, droplets can fly more than two metres – and even spread up to eight metres in exhaled air.
In a study published in the prestigious BMJ, they argued that social distancing rules should be updated to account for multiple risk factors, like indoor versus outdoor settings, ventilation, types of activity, and whether or not people are wearing masks.
For example, if you’re in a high-risk situation like a crowded bar or a nightclub, it would be wise to stand further than two metres away from others and to limit your time in that place.
In other lower-risk circumstances, like when you’re at a park or beach, less stringent distancing is likely to be enough.
Nicholas James, who co-authored the study, said the one-metre rule was based on over-simplified science that described the viral transfer of COVID-19 by either large droplets or small airborne droplets emitted in isolation, and without accounting for the exhaled air.
In reality, transmission of the virus was more complex, researchers said.
The virus’s spread depended on a variety of factors, including the difference in droplet sizes, viral load, duration of exposure, and the susceptibility of an individual to infection.
“Instead of single, fixed physical distance rules, we propose graded recommendations that better reflect the multiple factors that combine to determine risk,” they wrote.
“This would provide greater protection in the highest-risk settings but also greater freedom in lower-risk settings, potentially enabling a return towards normality in some aspects of social and economic life.”
The researchers said further work was required to decide how to best extend the social distancing rules to cater for different environments.
“Physical distancing should be seen as only one part of a wider public health approach to containing the COVID-19 pandemic,” they said.
“It should be used in combination with other strategies to reduce transmission risk, including hand washing, regular surface cleaning, protective equipment and face coverings where appropriate, strategies of air hygiene, and isolation of affected individuals.”