That is what really intrigues me. Japan is a case in point, especially Tokyo. High density population (Roughly 9 million in Tokyo). Yet, very low fatality rate and new cases rate. Sure there is less testing there. Also, the elderly population probably has fewer co-morbidities than many western nations, better hygiene, cleaner public restrooms, and a mask wearing culture. Many variables, of course, but it would be great if the different confounding factors could be analyzed/isolated to some degree.
Some have attributed these inter-regional differences to the BCG vaccination (TB). Many are skeptical. But at least they have started trials to see whether that vaccination could be a factor. (Nobody is expecting it to be a miracle cure, but at best, a temporary stop-gap measure, eg., less severe complications from pneumonia).
https://www.statnews.com/2020/04/14...icism-as-a-potential-weapon-against-covid-19/
I live in Los Angeles County with a population of 10 million. It currently runs around 900 new cases per weekday. This sounds so crazy for a County that is supposedly doing self-isolation, except for essential services.
http://www.publichealth.lacounty.gov/media/Coronavirus/locations.htm (Analyzing data from that link, almost 50% of the fatalities occurred in congregate living settings!)
Last Tuesday, Tokyo had "28 new cases of coronavirus infections Tuesday, Fuji News Network reported, marking a seventh straight day of single-day tally below 40."
https://www.japantimes.co.jp/news/2020/05/12/national/tokyo-28-coronavirus-tuesday/
That is quite a contrast. I hope it can be accounted for in the not so distant future.