Brownian motion in models for virus spread?
I read this article when it came out. I don't think the point is about whether or not people behave like particles in a fluid medium, but about how quickly people can spread the coronavirus when randomly interacting with one another in an open space (in my opinion, this model would be a reasonably good representation for a crowded area like a mall lobby or a beach where people are moving around more or less randomly).

However, even in other settings when people aren't moving around randomly, if anything, people are more likely to interact with each other in restricted spaces like sidewalks where there is less choice of where to position yourself spatially.