Britain’s two metre social distancing rule is based on outdated science and is not far enough in crowded places like bars, experts say.
Dr Nicholas Jones and colleagues at the University of Oxford said the rule was produced from studies dating back up to 100 years ago and is too simplistic.
Instead, there should be a grading system depending on how ‘risky’ a place is, they said.
Evidence suggests that how far virus-carrying droplets can spread from a cough or sneeze depends on the environment around them.
A bar, pub or nightclub would be deemed high risk because it is indoors, poorly ventilated and people have to shout to be heard over music. Therefore it should have more stringent distancing rules, the researchers argued.
But in places deemed to be low risk such as parks, the rules can afford to be relaxed, which would ‘potentially enable a return towards normality in some aspects of social and economic life’.
Scientists have previously argued the two-metre (6’7″) rule is not based on evidence but, in contrast to Dr Jones, were in favour of scrapping it.
Britons are told to distance themselves two metres from others, but in England and Northern Ireland this was reduced to ‘one metre plus’ in July in order to help pubs, restaurants and shops re-open.
The ‘plus’ refers to other efforts people should make to put barriers between themselves and others, such as not being face-to-face, screens, or face coverings.
The two metre physical distancing rule is based on outdated science and should be extended in crowded places like bars, experts have argued. Pictured: A group of drinkers enjoy the atmosphere in Manchester with takeaway pints of beer, July 4
A policeman keeps watch over the large crowds that gathered on the street in the middle of Soho in London, July 4
The researchers made a graphic to show the risk of SARS-CoV-2 transmission from people who do not have symptoms in different settings. A bar would be under ‘high occupancy, poorly ventilated, and without face coverings, showing even when no one is speaking, there is still a high risk
Social distancing is vital for reducing the spread of Covid-19 but is a contentious issue because it puts strain on the economy and relationships.
Dr Jones, a GP and researcher at the Nuffield Department of Primary Care Health Sciences, said the two metre rule can be traced back as far as 1897 and was supported by a range of studies in the 20th Century.
Despite the limitations of these early studies, they ‘assumed the scientific basis’ of the one/two metre rule now.
The paper noted a landmark review commission by the World Health Organization, which supported a one-metre-or-more rule to limit Covid-19 spread.
It was heavily based on data from the coronaviruses SARS and MERS, which are related to the virus that causes Covid-19 but are different and less deadly.
Scientists have previously said the WHO review used data of ‘poor quality’.
Another recent review of ten studies found eight showed projection of respiratory droplets beyond two metres – and even as far as eight metres (26ft) in one study.
Respiratory droplets are the main route of Covid-19 transmission, according to the World Health Organization (WHO).
Large droplets only travel short distances before falling to the floor, which is why it the ‘safe social distance’ recommended between people is two metres.
Aerosols, on the other hand, are small and can linger in the air for longer and travel further.
It is not clear yet if Covid-19 is airborne, but emerging evidence suggests it may play a role and is being reviewed by the WHO.
Dr Jones and colleagues said the two-metre rule is based on viral transfer by either large droplets or small airborne droplets emitted in isolation.
It does not account for the exhaled air that comes with coughing, sneezing, talking singing or panting – in a gym, for example.
All these generate warm, moist, high momentum gas clouds of exhaled air, which helps to move droplets faster than if they were isolated, keeps them concentrated, and can extend their range up to eight metres within a few seconds, the paper warned.
‘Clouds of small droplets can travel beyond two metres in the air, and even large droplets have enhanced range,’ the paper in the British Medical Journal said.
‘Rules… are based on an outdated, dichotomous notion of respiratory droplet size.’
Transmission is also impacted by the environment – including type of activity, indoor versus outdoor settings, level of ventilation and whether face coverings are worn.
Indoor case clusters have been reported within fitness gyms, boxing matches, call centres, and churches, where people might sing, pant, or talk loudly.
But they have not been linked with airplanes, where people are relatively silent.
Meanwhile an outbreak of cases at a Chinese restaurant was blamed on the ventilation, helping to spread the virus around.
And outbreaks in food factories have been attributed to a combination of cold conditions, poor ventilation, cramped working conditions, and background noise – which leads to shouting.
Other important factors include duration of exposure, susceptibility of an individual to infection and viral load of the transmitter, they said.
The paper argued: ‘Evidence suggests Sars-CoV-2 may travel more than two metres through activities such as coughing and shouting.
‘Rules on distancing should reflect the multiple factors that affect risk, including ventilation, occupancy, and exposure time.’
The authors called for more work to develop solutions to examine appropriate distances for people in different settings.
Instead of a one-size-fits-all approach to social distancing, there should be ‘graded recommendations’ for different distancing rules in different settings, they argued.
Pubs, bars and night clubs are the most risky and should have stricter social distancing rules, the paper said.
It did not give an example of a low risk scenario, but said the best conditions would be outdoors, in silence, with few people and face masks.
The researchers conclude: ‘Physical distancing should be seen as only one part of a wider public health approach to containing the Covid-19 pandemic.
‘It needs to be implemented alongside combined strategies of people-air-surface-space management, including hand hygiene, cleaning, occupancy and indoor space and air managements, and appropriate protective equipment, such as masks, for the setting.’
The paper noted a landmark review commission by the World Health Organization, which supported a one metre or more rule to limit Covid-19 spread. It was heavily based on data from the coronaviruses SARS and MERS, which are related to the virus that causes Covid-19 but arguably different. The study said keeping one metre apart can slash the risk of catching coronavirus by 80 per cent. But halving this gap raised the risk to only 2.6 per cent
The two-metre rule in England and Northern Ireland was reduced to ‘one metre plus’ in July in order to help pubs, restaurants and shops re-open. Pictured: How empty a pub would be with two-metre social distancing