In a new research published this Tuesday (23) in the scientific journal Physics of Fluids, scientists show that the distance of two meters to prevent contagion by SARS-CoV-2 is an arbitrary measure. This means that the airborne transmission of the virus is highly variable and can exceed this limit.
Researchers at Cambridge University, United States, used a computer modeling method to quantify how the droplets (from coughing or sneezing) spread. The team concluded that, without a mask, a person with covid-19 could infect another at a distance of two meters, even outdoors.
Still, the power of the cough also varies, so researchers point out that the distance could be anywhere between one and three meters or more. They wrote that “small droplets can be suspended in the air for a long time and can transport pathogens over significantly long distances, while larger droplets follow a ballistic trajectory and tend to settle quickly under the influence of gravity.”
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For Shrey Trivedi, from the Cambridge Engineering department, part of the way this disease spreads is virology — the amount of virus we have in our bodies, the amount of virus we expel when we talk or cough, and the other part is fluid mechanics.
Epaminondas Mastorakos, a professor in the Cambridge Engineering Department who led the research, said he heard a lot early in the pandemic about how covid-19 is transmitted, and the way it was spreading through door handles, for example . “I thought to myself, if that were the case, the virus should leave an infected person and land on the surface or disperse into the air through fluid mechanical processes,” he points out.
For that reason, since the beginning of the SARS-CoV-2 cases, health authorities have focused on hand washing and surface cleaning even in the early days — in addition to the use of masks. However, now, two years later, it is clear that the virus is spread through airborne transmission and infected people transmit it through coughing, speaking or even breathing, when they expel larger droplets that eventually settle in addition to aerosols. smaller ones that can float in the air.
To understand how virus transmission can take place beyond two meters, the scientists ran a series of simulations. For example, if a person coughed and emitted a thousand droplets, they calculated how many of these hit another individual in the same room and how big those droplets would be, as a function of time and space.
As a result, they concluded that there is no abrupt break from two meters. This way, if the person coughing is not wearing a mask, the larger droplets fall in close proximity. On the other hand, the smaller ones spread easily — depending on the speed and distance, in addition to the quality of the space’s ventilation, easily surpassing this pre-established footage.
The researchers say that while the two-meter rule is easier for people to remember, distancing alone is not a fully effective measure. This highlights, according to them, the importance of vaccination, ventilation of public spaces and the use of masks.