[gridlockd]

Of course there's lots of factors, but this is one obvious factor that must not be ignored.

> What about different strains and variability in how deadly they are?

Is there any evidence that the variations spreading now are different from those spreading earlier this year?

> What about the difference that the size of the initial dose of the virus makes to the end outcome?

There was a study done on hamsters that only showed a minimal impact of initial dose on disease severity.

On the other hand, you have increased mortality among healthcare worker, which could be caused by higher exposure. However, there's also the impact of such a stressful situation on the immune system.