There is a huge difference between two people passing and hundreds of people staying put at that distance for an hour.
It really comes down to the math and the density not just of interactions, but of secondary and tertiary interactions.
Draw a line between every person that interacts with every other. Make it a bit darker if no facemarks for the possibility that one is already infected and doesn’t know it. Darken that line a bit more for each person that either comes into contact with later, and maybe half as much again for each person that they come into contact with.
The darker this map becomes, the more opportunities for infection.
To stop it doesn’t require removing all of these, but by making the map light enough.
Ultimately, the “R”, the average number of infections stemming from each infection, needs to drop below 1. The further below 1, the faster it dies off. Above 1, the level of infection increases.
The base level, R0, is notably higher for this disease than for other recent ones, as well as common ones.