Earlier quoted context omitted.
There isn’t any reason to believe the virus kills a resident of NYC any easier than it kills a resident of Kansas if either is infected with it. NYC is an excellent example to look at precisely because of what you said - it’s a dense population center and international travel hub, so it was seeded with quite a few coronavirus cases early on and unfortunately the virus seems to have infected up to 20% of the residents…
The infection rate relevant insofar as it means the population will approach 100% infection [1],- and subsequent immunity or death - faster than other regions. Densely populated areas like New York will have a sharp spike and sharp decline. Loosely populated areas like Kansas will see a slower, steadier rise but also a slower and steadier decline. Social distancing makes areas behave more like rural areas, by virtue…
Yes, if by approaching you mean at least twice the number of people who have already died from the virus would have to die to achieve this, since 20% is less than half of 50%. I’ve seen scientific experts estimating that with this specific virus, due to its high R0, 50-70% is not the threshold for herd immunity anyway and it could be up to 84% or higher (Polio = 80%, Measles = 95% thresholds, for comparison). That could mean up to 4x the amount of deaths we’ve already seen.
The total number of people who would be affected by a herd immunity strategy could also be changed by a social distancing intervention around the time the threshold is reached. Otherwise, models indicate there would be an overshoot and a higher % of people would end up being infected than is necessary for herd immunity. No country or region seems to have reached this threshold yet though since they all engaged in social distancing first. https://twitter.com/CT_Bergstrom/status/1252078649827667968
The other option would have been to do what several countries in the Asia Pacific region did - Taiwan, Vietnam, and apparently China, for instance. Instead of allowing the virus to run free, they have worked toward eliminating it within their borders. Many lives will be saved if that plan can succeed and they can avoid a “herd immunity” result until a safe vaccine is available to provide the herd immunity.