Based on the scant reading I've been doing over the past two months, it looks as if maybe (please note the emphasis) people who are only lightly exposed to Covid-19 are less likely to get the disease, less likely to suffer as much from it, and less likely to die from it than are those who are very heavily exposed to it. They still get it, but not as seriously or maybe even asymptomatically.
This is all probabilistic of course. As well, there are very likely many other determinants of getting infected, the seriousness of the infection, and death.
But suppose that roughly speaking, probabilistically , in general, it's correct. If so, it has some important implications:
1. Social Distancing
Why the 6' line of demarcation? Surely potential droplet and aerosol contamination isn't binary. What about 5'10"? what about 6'3"? Is it possible that if people stay farther apart, the result is that if they happen to get a few virions of CV19 into their bodies, it's not enough to make them seriously ill, ceteris paribus? Is it possible that people who are closer to a carrier are more likely to be bombarded by more virions because their are closer to more people, and it's the number of virions per some unit of time that determines everything? I don't know how viri and virions work.
2. Masks
Why are some masks recommended in some situations and not others? Maybe it depends on both the likelihood and strength of the potential bombardment?
Front-line health workers may very well need N95s or the equivalent because they are constantly and heavily bombarded, and even with N95s, a few virions get through, but not enough to cause serious damage (in most people; remember this is probabilistic).
So if I walk past someone who is a carrier, they might expel a droplet or an aerosol containing the virus, but if that's it, I might not get the disease because of the low bombardment, or I might get a low-grade infection because my body can fight it off at that level? But if I'm at a restaurant, sporting event, concert, play etc. (pre bans, of course), I'm more likely to be more heavily bombarded and more likely to be infected and more likely to suffer more seriously?
If these guesses are correct, then maybe even wearing a t-shirt or bandana mask might not only protect others from me if I am infected, but will also, at the margin, protect me by somewhat lowering the rate of bombardment that would get to my lungs. This might work when I'm walking on trails or along the sidewalk or in environments which assiduously practice social distancing, etc. [e.g. the Blood Donor Clinic].
But if I'm in a grocery store, where who knows what is in the air and on the products, maybe I face a higher risk of heavier bombardment? And if so, in those environments I might be better advised to trim my beard so an N95 mask fits better and wear that mask.
3. Hospital Workers
People working nowhere near CV19 patients might be okay with just surgical masks if all my above hypotheses are correct. They're unlikely to be heavily bombarded by virions or by many. The surgical masks will stop enough to leave most of those workers ok.
But others working with ER and CV19 cases are more likely to need N95s or better just to reduce the number of virions that get through to them.
The whole point, here, is that protective measures don't just reduce the probability of being infected by CV19 virions; they also reduce the bombardment effect -- they reduce the number of virions that get through to my lungs, etc., and thus leave me less less likely to be symptomatic, or, if symptomatic, with the effect that I would suffer less and be less likely to die.
I.e., it's not just the probability of being hit and infected by a virion, but it's the density and severity of the intake of the virions.
I may be right out to lunch. After all, I'm not a virologist, Jim.