Transmission Risk as a Continuum

I’ve written before how risk of exposure to SARS-CoV-2 (the virus that causes Covid-19) is a continuum and that there are no exact risk thresholds for say duration of contact or appropriate distance. For instance, wearing a mask reduces risk but doesn’t eliminate it. It is the same with distancing. 6ft may not be sufficient indoors with poor ventilation when someone is talking loudly or singing.
Often, multiple things have to be happening at the same time, and the risk is not equal in every setting and activity. Prolonged contact, poor ventilation, highly infectious person, crowding are the key parameters, in addition to face coverings (and type), distancing and activity (screaming, singing etc). A combination of the above decided the risk and it can vary based on the accumulative effects of all of these.
Here is a helpful chart:


For futher reading, see my post here:


Unambiguous Science