Another great example is the outbreak in a call center (see diagram above; people who got infected are in blue). A single infected employee came to work on the 11th floor of a building. That floor had 216 employees. Over the period of a week, 94 of those people become infected (43.5%: the blue chairs). 92 of those 94 people became sick (only 2 remained asymptomatic).This is because time is a key factor. You are not very likely to get infected from being near a carrier for a brief interval, but sharing the same air for eight hours a day will get you.
Indoor spaces, with limited air exchange or recycled air and lots of people, are concerning from a transmission standpoint. . . . Social distancing guidelines don't hold in indoor spaces where you spend a lot of time, as people on the opposite side of the room were infected.Restaurants can also be very bad, because people may sit near each other for an hour or more.
In all these cases, people were exposed to the virus in the air for a prolonged period (hours). Even if they were 50 feet away (choir or call center), even a low dose of the virus in the air reaching them, over a sustained period, was enough to cause infection and in some cases, death. The principle is viral exposure over an extended period of time.
I highly recommend reading the article. As for me, this confirms my intention to keep working from home until this is all over, and also not to ride public transit or eat in restaurants.