Understanding the key concepts of transmissibility and infectious dose should reassure you.
Sigal SamuelApr 24, 2020, 8:00am EDT
Under social distancing, we’re all doing our best to stay sane, and one of the best ways to maintain sanity is to go out for some nice fresh air. But venturing outside can be stressful if you’re worried that the very air is full of virus particles just waiting to infect you.
So, how worried should you be that any time you go outside, you’ll contract coronavirus from a fellow pedestrian, runner, or cyclist who happens to exhale as they pass by?
The answer is, you probablydon’t need to freak out about it. As long as you’re maintaining at least 6 feet of distance from other people and you’re not in a high-risk group, you’re engaged in a very low-risk activity, particularly if you and others are wearing masks.
Earlier this month, Belgian-Dutch engineers publicized some findings that went viral online and gave people the opposite impression. The engineers used a spray nozzle particle generator to simulate the spread of droplets we generate as we walk, run, or bike. Since the particles hit a trailing athlete who was farther than 6 feet away, the engineers concluded we need to maintain more distance than that to avoid the risk of contracting Covid-19.
They recommended staying 16 feet behind someone who’s walking, 33 feet behind someone who’s running or biking slowly, and 65 feet behind someone who’s biking hard. Those sorts of distances are almost impossible to maintain in big cities. So, as the findings made the rounds online, lots of people panicked.
But this research — despite being branded as a “study” in a much-shared Medium post aiming to summarize it — contained no input from epidemiologists or virologists and was not peer-reviewed. Its logic is deeply flawed.
“I think we should be very careful with making assumptions about transmission based on that ‘study,’ since it didn’t account for any variables related to transmissibility,” said Angela Rasmussen, a virologist at Columbia University, adding, “It’s important to understand that infections are started with a minimum infectious dose of virus.”
In other words, the “study” failed to consider two key questions: How easy is it for particles traveling in the air outdoors to infect you? And how many particles containing infectious virus would you have to inhale to become infected?
The engineers simply concluded that any exposure was too much. But that’s not the case; the truth is more reassuring. Let’s break down each of the two questions in turn.
How easy is it for particles traveling in the air outdoors to infect you?
To start with, we should get clear on something that has proven confusing to lots of people: Is the coronavirus “airborne”?
Getting coronavirus from runners, cyclists, or air outside is unlikely – Vox
Understanding the key concepts of transmissibility and infectious dose should reassure you. Sigal SamuelApr 24, 2020, 8:00am EDT Under social distancing, we’re all doing our best to stay sane, and one of the best ways to maintain sanity is to go out for some nice fresh air. But venturing outside can be stressful if you’re… [Read More]