New model of physical distancing
The authors of the BMJ study developed a new guide to physical distancing that takes many of these factors into account. They use three colors to indicate the relative risk of being exposed to the coronavirus in different settings.
For example, at a backyard party where people can stay far apart from each other and everyone is wearing a mask, the risk is low. People can stay here for an hour or more and still be at low risk. They can even shout or sing if they want.
However, if people take off their masks, this setting is only low in risk if they aren’t shouting or singing because the masks are no longer slowing down the cloud of expiratory droplets. And people can only stay there for a long time without a mask if they aren’t talking.
“If you’re wearing a mask, the 6-foot rule would be quite effective,” said Capecelatro, “but if you’re not wearing a mask, then you can certainly [contract the virus] at distances beyond 6 feet.”
Likewise, if people crowd into a backyard, the only low-risk options involve wearing a mask. In addition, many — but not all — of the high-risk settings involve spaces that are crowded or poorly ventilated.
The BMJ guide is similar to one created by Dr. Ezekiel J. Emanuel and colleagues, which provides more examples of specific activities.
The key thing to both of these guides is that COVID-19 risk varies across settings. Bourouiba’s approach, though, emphasizes that 6 feet may not always be enough to keep your risk low.
“The general rule of thumb is that keeping a distance from someone decreases the probability that you’re going to be breathing in droplets that they expelled,” said Capecelatro. “And while we’ve been using the 6-foot rule for a long time, we know that you should probably be at least twice that distance away to be more certain.”
Source : Healthline