Consider this. The coronavirus may very well have been endemic in Asia for many thousands of years. Therefore the endemic human population has had to deal with its presence and its mutations. It is therefore logical to assume that the modern day Asian population are the descendants of those who possessed the genetic capability to deal with and survive coronavirus infections. Much the way after thousands of years of exposure to pastuerella pestis (plague), the modern European population has little susceptibility. ( ever wonder why plague did not break out in the concentration camps, POW camps and the unhygeinic, starved cities during WW II). Also may explain why COVID-19 has not spread throughout China to the extent it has elsewhere. The Chinese have the genetic capability to deal with most coronavirus. Could be the reason their biological warfare experts viewed the corronavirus as a logical weapon. Most Chinese would be inherently immune while non Chinese enemies would likely be very susceptible.