Rigid Covid-19 social distancing measures are based on "outdated science" with experiences of past viruses, a report published in the British Medical Journal said.
In the report, scientists at the University of Oxford, Massachusetts Institute of Technology and London's St Thomas's Hospital said rules that ensure people stay one or two metres apart are based on viral transfer by large droplets or small airborne ones.
But they do not account for the exhaled air that carry them.
The World Health Organisation advises people to keep at least a one metre apart from others to ensure the coronavirus does not spread, up from an earlier two metres.
But the report's authors say transmission is more complex.
The origins of the two-metre rule date to the 19th century and early studies took it as the baseline for most airborne contagious diseases.
But recent evidence indicates that small water droplets carrying the coronavirus can travel more than two metres by when released through coughing and shouting.
They can spread up to eight metres concentrated in exhaled breath from an infected person.
If the person is silent, however, the risk is much lower in most settings.
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A parrot stands on a girl's shoulder on the first day after Giza zoo reopened amid the coronavirus pandemic, on the outskirts of Cairo, Egypt. Reuters -
A man feeds llama on the first day after Giza zoo reopened amid the coronavirus outbreak, on the outskirts of Cairo, Egypt. Reuters -
People queue outside a bakery following an announcement calling for the closure of public spaces across the Gaza City amid rising number of coronavirus cases. AFP -
A Palestinian security officer speaks to a man following an appeal for shutting down public spaces across the Gaza City amid the rising number of coronavirus cases. AFP -
A member of the Palestinian security forces monitors shoppers queuing for bread after the announcement of restrictions in the Gaza City amid rising numbers of coronavirus cases. AFP -
A robot designed by Egyptian engineer Mahmoud El Koumy collects swab for coronavirus testing, in Tanta, about 100 kilometres north of Cairo, Egypt. EPA -
Egyptian mechatronic engineer Mahmoud El Koumy presents a robot that he created and is capable of taking a blood sample for the diagnosis of Covid-19, in Tanta, about 100 kilometres north of Cairo, Egypt. EPA -
A worker wearing a face mask presents a handful of harvested jasmine flowers in a field at the village of Shubra Beloula in Egypt's northern Nile delta province of Gharbiya. AFP -
Palestinian women and children wearing masks walk in an alley in the Old City of Jerusalem. AFP
Other recent studies suggest that recent related viral outbreaks such as Sars, Mers and Avian flu can spread beyond two metres.
The scientists suggest distancing rules need to take account of several factors that affect risk, including type of activity, whether settings are indoors or outdoors, ventilation levels and whether face masks are worn.
The concentration of virus the emitter is carrying, how long they are exposed to the coronavirus and the susceptibility of a person to infection are also important factors.
The authors propose graded safety recommendations based on those factors.
“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,” they said.
Transmission risk will vary depending on settings.
In the highest risk situations, such as a crowded bar or nightclub, physical distancing beyond two metres and minimising the times people are allowed to stay should be considered.
Less stringent distancing is likely to be enough in low-risk scenarios, such as sparsely populated outdoor spaces.
“Physical distancing should be seen as only one part of a wider public health approach to contain the Covid-19 pandemic,” the authors say.
“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.”
Earlier on Tuesday, Prof John Bell, part of a team of University of Oxford researchers working on a promising potential vaccine for the coronavirus, said he was optimistic that data proving its effectiveness would be available to regulators as early as this autumn.
