Asymptomatic transmission is the concept in question. Symptomatic transmission is the typical case -- you cough, sneeze, etc., and give it to others. There's s

Asymptomatic transmission is the concept in question. Symptomatic transmission is the typical case -- you cough, sneeze, etc., and give it to others. There's still quite a bit of debate over this question, despite the article's insistence that the matter is settled. The data supporting it comes mostly from modeling studies, and real-world data is thin on the ground. Mostly anecdotes. We have lots of examples of pre-symptomatic (or minimally-symptomatic) transmission for other illnesses, but these tend to be limited (e.g. spread within households), and it's always been a bit of a stretch to make the claim that completely healthy people are spreading diseases widely in "super-spreader" events via casual encounters. Does it happen? Sure. Is it common? Ehhhh. Even with Covid, we know that the majority of transmission (something like 80%) occurs within households. Of the remainder, as TFA notes, there's an "overdispersion", where a few people are responsible for most of the spread. Is it really likely that these "superspreader" people are mostly completely healthy, without symptoms, and yet unknowingly spreading it to vast numbers of people? Or is that just something that we've found a few times, and makes the most memorable anecdotes? It is certainly not the hypothesis you would favor based on parsimony alone. If you were a betting person, you'd probably put your money on the idea that someone is a little bit sick (but not so sick as to stay home in bed), and the disease can spread by aerosol or droplet with low probability. That's a much simpler explanation for the same pattern: someone has a tickle in their throat or a slight fever, but goes to the restaurant/office/wherever anyway. Set the probability of transmission to a low p-value, and let the poisson distribution do the rest. Just by chance alone, you will see rare occasions where large(r) groups of people get infected.