As opposed to most things I read on this topic, I found the following three quotes from epidemiologist Michael Osterholm informative on understanding the way the virus spreads.
I don't worry about food. I don't worry about newsprint. I don't worry about packages I get here. I don't worry about doorknobs and railings any more than I would during the regular cold season. [That's not] what's going to be the major challenge with this virus. ... It's the air that we share with each other that is critical. That's why distancing is so important.
On air flow:
Right now, we have to understand that the single greatest risk factor we have for transmitting this virus is largely indoor air, where we're in large crowds, where we are sharing that air with the people right around us.
On exposure time:
I think people often think of transmission with this virus almost like tag: I get close to somebody who's infected — "Tag! You're now it." It's not at all. It is time related. We're working on this, and it may be that you need many minutes to be in an environment where this virus is in the air and you need to inhale it in, and the amount of breathing that you do at a certain level before you get infected, it's not just a yes or no. It's a threshold.