- Most guidelines suggest a distance of around 2m between people to help curb the spread of Covid-19
- Now, researchers point out that this rule is based on research done in the 19th century
- They also state that droplets can travel further than 2m, but that it depends on several factors
Currently, regulations in many countries stipulate a distance of 2m between people in any public setting as a non-pharmaceutical intervention to contain the spread of Covid-19.
New research published in the BMJ states that rules that stipulate a certain distance between people are based on rigid, outdated science that doesn’t account for the complexity of SARS-CoV-2.
According to Nicholas Jones, main author from the University of Oxford, rules based on one single distance are based on an over-simplistic dichotomy describing viral transfer by either large or small airborne droplets emitted in isolation without accounting for exhaled air.
Despite the 2m rule being established in current guidelines, transmissions depend on many other factors. Evidence suggests that droplets expelled by e.g. coughing or shouting may spread as far as seven to eight meres.
Why was the 2m rule established in the first place?
The study of how droplets are emitted during speech, or with more force by coughing or sneezing, dates back to the 19th century. In 1897, a 1 to 2m distance was proposed as sampled visible droplets were tested by using agar plates or glass.
A study in 1948 showed that in the spread of haemolytic streptococci, fewer than 10% of the participants produced droplets that travelled further than 1.7m – once again establishing that 2m is a safe distance to contain the spread of pathogens from one person to another.
These studies, however, had their limitations, and according to the researchers, a recent systematic review shows that respiratory droplets have the ability to travel well over 2m.
In the research, Jones suggests that distancing rules need to take into account multiple factors that can affect risk such as indoor versus outdoor settings, the level of ventilation and whether face masks are worn in a particular setting.
The research also takes into account that viral load, the length of exposure to different people and an individual’s susceptibility to contracting Covid-19 can play a role.
"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 stated.
In higher-risk situations such as night clubs or crowded bars, physical distancing of more than 2m should be considered, while low-risk situations require less stringent distancing.
"Physical distancing should be seen as only one part of a wider public health approach to containing the Covid-19 pandemic. 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," the researchers said.
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