In 2018 China knew there was a problem, but did not know the extent of it, and hid their response from the world. Since it's seasonal, it mutated and resurfaced in May 2019 & sent PLA into emergency response mode.
— Ethical Skeptic ☀ (@EthicalSkeptic) October 4, 2021
Too late however as it already was in Japan, Taiwan, Korea, etc. pic.twitter.com/D5e3RUyHxl