From a CNN posting about the Olympics:

Linsey Marr, an engineering professor at Virginia Tech and an expert in how viruses behave in the air, said that cigarette smoke is a great way to visualize the most up-to-date understanding of how the virus lingers and how easily it can be spread. "Because it comes from our mouths and carries particles that are similar in size and behavior to the virus," she said.

If you imagine an infected person exhaling the virus as smoke and watching that vapor drift easily in the air, it will forever change how you think about protecting yourself and others.
The much more contagious Delta variant, which has grown at least seven-fold in Japan since the start of June, compounds the problem.

"So before, it was like an infected person was smoking one small cigarette at a time, but now it's like they're smoking a few cigarettes at once because we think they shed more virus. More smoke means that more will still be in the room even after the person has left. After the person leaves, the smoke becomes diluted as outdoor air replaces some of the indoor air, but if there was more to begin with, then there will be more 15 minutes after the person leaves," Marr said.

[link:https://www.cnn.com/2021/07/24/health/olympics-during-pandemic-gupta/index.html|