In reply to Cobra_Head:
china has the monopoly on these things because it covers so much ground. 1/5 the population with such massive industries catering to the other 4/5 in a swirl of activity across just about every environment at stunningly interconnected speed. one sick pig in Guizhou can be infecting an entire market in Dalian the next day. then with so many international hubs the chance of getting it out and directly into a foreign city of 10 million is enormous.
whatever the optimum virulent environment is, China will have a lot happening in and the connectivity to push variation about. that sick pig may reached slaughter harmlessly in the dry north west, but trucked to the humid coast things go literally viral.
on a scale of insanity tho, its all just training for the real chaos that comes after the US election, whatever the result. good way to see how systems hold up.