>The BIGGEST clue is that it is barely affecting the young.
This is fairly typical of chest cold in general. When you hear of someone being hospitalized for pneumonia you usually think of an elderly person.
A second clue is that it affects males more than females. The big difference between these two groups is smoking.
https://qz.com/521662/68-of-chinese-men-are-smokers-and-millions-will-die-because-of-it/