You’re unlikely to get COVID from runners or cyclists
Snippet from article written by Sigal Samuel, for Vox
Many of us saw the findings published last month by Belgian and Dutch engineers that suggested maintaining specific (and far) distances from bikers and runners when you're outside, but the study failed to consider two key questions:
How easy is it for particles traveling in the air outdoors to infect you?
How many particles containing infectious virus would you have to inhale to become infected?
Jennifer Kastenm, a pathologist with training in infectious disease epidemiology and global health and Angela Rasmussen, a virologist at Columbia University, both noted that a perfect sequence of events has to happen for a virus to jump from an infected passerby outdoors to you.
"The particles — enough of them to be able to kickstart an infection — have to spray out of the passerby with enough force to make their way over to you. The virus inside the particles has to survive while sunlight, humidity, wind, and other forces work to decay and disperse them. The particles have to land right in your upper throat or respiratory tract — or on your hands, which you then use to touch your eyes, nose, or mouth — and they have to get past all the barriers to infection in the respiratory system, like nose hairs and mucus. Then they have to dock up with your cells’ ACE-2 receptors and use them to enter the cells."
This article from Vox also examines how long a surface is infectious and the impact of certain variables like temperature, humidity, etc.