4 ms·

Yeah but isn't this impossible? People go to the grocery store and come into contact with hundreds of people in an hour.

tzs 6y ago
For most viruses whether or not you get sick or become infectious after being exposed to them depends on how strong the exposure was. The amount you need is called the infectious dose. The infectious dose of COVID is not known, but believed to be somewhere in the several hundred to a thousand viruses range. An infected person breathing normally near you might expose you to something like 20 or 30 per minute (breath is normally expelled with low force, so it doesn't contain viruses from the lower parts of the respiratory tract). Talking might do around 200 per minute. A cough or sneeze can do millions. Thus, if I have COVID and go shopping at the same time you do, wearing a mask, and don't cough or sneeze pretty much in your face when we happen to pass each other, you almost certainly are not going to get it from me, and it makes little difference for contact tracers to find you. It is the people that I spend a few minutes talking face to face to or that I spend a long time near that contact tracers need to find. Note that it doesn't depend on who you get the viruses from. If a lot of people in the grocery store have it, then even though you might only get a handful of viruses from each person you pass you still might accumulate an infectious dose during your time in the store. To control it, you need to get the number of infections down enough that people won't be getting it from casual transitory contact, like when grocery shopping, and people need to limit situations that involve more extended contact to times/places where the people they have extended contact with can be identified and traced, and need to limit the frequency of those events so that there is time for contact tracing to work.
- nickthemagicman 6y ago
  "The infectious dose of COVID is not known" You could have stopped there.

tzs 6y ago

For most viruses whether or not you get sick or become infectious after being exposed to them depends on how strong the exposure was. The amount you need is called the infectious dose. The infectious dose of COVID is not known, but believed to be somewhere in the several hundred to a thousand viruses range. An infected person breathing normally near you might expose you to something like 20 or 30 per minute (breath is normally expelled with low force, so it doesn't contain viruses from the lower parts of the respiratory tract). Talking might do around 200 per minute. A cough or sneeze can do millions. Thus, if I have COVID and go shopping at the same time you do, wearing a mask, and don't cough or sneeze pretty much in your face when we happen to pass each other, you almost certainly are not going to get it from me, and it makes little difference for contact tracers to find you. It is the people that I spend a few minutes talking face to face to or that I spend a long time near that contact tracers need to find. Note that it doesn't depend on who you get the viruses from. If a lot of people in the grocery store have it, then even though you might only get a handful of viruses from each person you pass you still might accumulate an infectious dose during your time in the store. To control it, you need to get the number of infections down enough that people won't be getting it from casual transitory contact, like when grocery shopping, and people need to limit situations that involve more extended contact to times/places where the people they have extended contact with can be identified and traced, and need to limit the frequency of those events so that there is time for contact tracing to work.

nickthemagicman 6y ago
"The infectious dose of COVID is not known" You could have stopped there.