In this case the Chinese knew, in early December, they had a problem when they only had a handful of cases. HOW????
COVID presents like the flu, so there isn't a novel symptom to help them identify that something new is in play.
There wasn't a significant rise in cases or deaths. There couldn't be a significant rise in deaths because there weren't that many cases. A small cluster of flu cases escalating into pneumonia, and then death won't raise a red flag because it happens all the time. I've had multiple Chief Medial Officers tell me this.
With COVID presenting like the flu, and with so few cases the ONLY way they could know that a new virus was spreading was if they had prior knowledge. The only way they could get prior knowledge was because someone working at the lab got sick, and then people they came in contact with got sick.
If this really happened organically then it should have been spreading pretty damn fast, and because it presents like the flu it wouldn't have raised any eyebrows until either the case rates spiked or the death rates spiked. In the U.S. flu cases per year range from a low of 9.3M to a high of 45M and deaths of 12,000 up to 61,000.
I suspect that China sees the same fluctuations in yearly flu cases so localized spikes wouldn't have raised any eyebrows it wouldn't have gotten anyone's attention until hospitals started to get overwhelmed. But in early December they didn't have that many cases.
So how did they know?