> The number of diagnosed cases or positive test results is only loosely correlated with the number of actual infections.

Then that just means that we are likely underestimating R0--possibly by a huge amount. Okay, I agree with you.

Infections aren't LESS than the diagnosed cases and positive test results. So, all the calculations from data about the estimates of R0 are all a lower bound, not an upper one.

As such, our estimates of R0 are likely painting a much rosier picture than reality. Probably not the point you were trying to make.

You missed the point. There are a lot of cases which are never formally counted as "cases" because people recover without ever being diagnosed. We don't know whether that fraction of unreported cases has increased or decreased over time. Outside of a few limited areas there hasn't been enough random population sampling to draw any reliable conclusions one way or the other.

You have just said that we probably have quite a few cases of Covid which are not counted and are not part of the model because they were undiagnosed. I agree.

If we somehow magically started accounting for those cases the R0 would immediately go up (more cases per unit time means increased R0) unless the number of those cases is zero.

Thus, the R0 estimates we have are currently all underestimates. Covid is likely more contagious than we are calculating, not less.

Now, this doesn't matter to the people who recover, of course. And it effectively is correct in that people who simply recover aren't a big problem and so the R0 is roughly "correct" in the aggregate.

However, that incorrect R0 DOES matter when you start talking about vulnerable populations and how far you need to go to protect them.

R0 does not exist outside of context either. We like to think to R0 has being whole numbers. R2, R4 etc. Or small decimals.. R1.5.. But really, _everyone single person that gets infected_ actually lowers R0 a tiny bit, as they are now recovered. Combine this with the late breaking evidence that there is some cross reactive immunity in T cells with other coronaviruses, and we see that R0 is completely meaningless without more data. If R0 is a lot higher, lets say 7.5 or some absurd amount, and we do have such a cross-reactive immunity, herd immunity may come at 40%. See, it needs context.