Maybe this is demonstrates an immediate consequence of having a people (mainland China, not necessarily HK) that is governed primarily by fear: reactions of extreme subordination, which keep things running "smoothly" under normal conditions, can threaten the whole system to collapse under abnormal conditions.
It's more of a cultural reaction that many went to the shop to gather food, detergent, face masks and more for the next month(s) so the shops have run out of things (plus many businesses and transports have closed). The panic wasn't driven by government decision but by people acting individually in concert.
It's hard to tell if the same would happen in the US or Europe if and when the first few people will get infected by the virus.