If the virus has spread to 0.01% of the population (33k cases), a stadium with 6932 people in it has a 50% chance of having at least one infected person in it (

If the virus has spread to 0.01% of the population (33k cases), a stadium with 6932 people in it has a 50% chance of having at least one infected person in it (assuming uniform distribution). If the virus has spread to 0.1% of the population (330k cases), an auditorium with 693 people in it has a 50% chance of having at least one infected person in it. If the virus has spread to 1% of the population (3.3M cases), a cafeteria with 69 people in it has a 50% chance of having an infected person. If the virus has spread to 10% of the population (33M cases), a house or office with 7 people in it has a 50% chance of having an infected person. If the virus has spread to 50% of the population (165M cases), a fortified secret bunker with 1 person in it has a 50% chance of having an infected person. But if that bunker dweller hunkered down back when the spread was only at 0.01%, not only would they have less chance of being infected themselves, they would also not be potentially spreading it to others. So it pays to start limiting contacts earlier.