The world did know. Do you really think our intelligence agencies didn't know exactly what was going on? We have satellites looking at every inch of China and operatives on the ground all over China. The U.S. and world intelligence apparatus knew and so did every world leader including the U.S. President. They all either just didn't believe it or took the risk that it wouldn't be as harmful to them getting re-elected as shutting down their national economies.
It didn't filter down to lower level leaders like Governors, etc. But, heads of state had to know.