3 ms·
Technically, yes, there is an R0 above which a virus is self sustaining. But if something has R0 of 1.25 the herd immunity threshold is about 20%, whereas if it
by cameronh90 7y ago
Technically, yes, there is an R0 above which a virus is self sustaining. But if something has R0 of 1.25 the herd immunity threshold is about 20%, whereas if it's 18, the HIT is nearly 95%. Additionally, R0 isn't an absolute property of the pathogen, so even assuming there is this absolute HIT, if R0 is around 1, some people will be above 1 and some below 1.
As herd immunity increases, the R0 decreases. A disease with a low R0 spreads more slowly (hence the logistic curve) and is therefore easier to track and trace manually, and has a lower peak and total infection count.
I don't think this is binary at all, or even _that_ stark of a threshold. Transmission doesn't continue at the same exponential rate until it hits around 60% and then suddenly disappear. It doesn't even come close to approximating that behaviour.