Thanks. Really informative. Here's link to article in his tweet (because I somehow missed it in the tweet): https://www.theatlantic.com/health/archive/2020/09/k-overlooked-variable-driving-pandemic/616548/ It says that people are getting it at large events/gatherings. If one person has it there and goes to the event, they spread it to a lot of others. Typically these large gatherings are loud so people will take of their mask or speak loudly. This causes the virus to spread quickly to many people. Other people who get it and don't go to large gatherings are less likely to spread it as they aren't talking loudly and are less close together.