The 6-foot social distance rule does not protect against COVID-19, whether indoors or outdoors

CAMBRIDGE, United Kingdom ( – Although the “six-foot rule” has been an integral part of the coronavirus security measure since 2020, does it really do anything to keep people healthy? A new study finds that the answer to that seems to be a resounding no. Researchers at the University of Cambridge say the six-foot social distance rule does not protect against capturing COVID-19, not even outdoors.

The team is calling rule of social distance a “random measurement” of safety in the absence of masks. It could have been set somewhere between 3 and 10 feet, depending on the risk tolerance of the local public health authority issuing the mandate.

Infected individuals spread the virus through coughing, speech, and even breathing. People emit larger droplets that eventually settle on surfaces or break into smaller aerosols that can float through the air. The study used computer modeling to quantify how these infectious particles rise. Results show that coughing varies a lot when it comes to expelling particles.

“I remember hearing a lot about how COVID-19 spread via door handles in early 2020, and I thought to myself that if that were the case, then the virus would have to leave an infected person and land on the surface or spread in the air through liquid mechanical processes, ”says lead author Professor Epaminondas Mastorakos in a university publication.

No masks lead to an unknown dynamic of coughing

Researchers say that the results in Physics of liquids emphasize the continuing importance of vaccination, ventilation and masks on the road to winter.

Early in the pandemic, health experts focused on hand washing and surface cleaning. However, Cambridge engineers note that it has been clear for almost two years that COVID is spreading airborne transmission. They have developed various programs to study how the virus behaves in different environments.

“Part of the way this disease is spread is virology: how much virus you have in your body, how many virus particles you expel when you talk or cough,” adds lead author Dr. Shrey Trivedi. “But another part of it is fluid mechanics: what happens to the droplets when they are first expelled, and this is where we come in. As specialists in fluid mechanics, we are like the bridge from the emitter’s virology to the receiver’s virology. And we can help. risk assessment. “

Simulations showed how much of the virus would reach another person in the same room from a cough containing 1,000 drops. The researchers found that there is no sharp cut once the droplets are spread out over two meters.

When a person coughs and does not wear a mask, most of the larger droplets will fall on nearby surfaces, but smaller droplets suspended in the air can quickly and easily spread far beyond the six-foot mark. How far and how fast these aerosols disperse will depend on the quality of ventilation in a room. In addition to the variables around mask wearing and ventilation, there is also a high degree of variation.

“Every time we cough, we can emit a different amount of fluid, so if a person is infected with COVID-19, they can emit many virus particles or very few, and because of the turbulence, they spread differently for each cough,” Trivedi continues.

The 6-foot rule may only be good for COVID messages

The team’s calculations took into account turbulent flow and detailed descriptions of droplet motion and evaporation.

“Even if I expel the same number of drops every time I cough because the flow is turbulent, there are fluctuations,” says Mastorakos. “If I cough, fluctuations in speed, temperature and humidity mean that the amount someone gets at the two-meter mark can be very different each time. “

The six-foot rule is an effective and easy to remember message to the public. However, the study finds that is not a security mark given the large number of variables associated with an airborne virus. Vaccination, ventilation and masks – even if they are not 100 percent effective – are essential to limit the pandemic.

“We are all desperate to see the back of this pandemic, but we strongly recommend that people continue to wear masks in indoor spaces such as offices, classrooms and shops,” Mastorakos concludes. “There is no good reason to expose yourself to this risk as long as the virus is with us.”

The researchers perform similar simulations for rooms as lecture halls to assess the risk as people spend more time indoors. The World Health Organization recommends a distance of at least three feet (one meter) from others – even if they do not appear to be ill. The WHO also advises people to avoid crowds and close contact and to wear a properly fitted mask in poorly ventilated rooms.

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