> Look, (I am assuming here) neither you nor I know how a new strain of a flu is detected
I worked on flu surveillance and monitoring projects for 3 years, and have a forecasting paper published in PNAS (although that was for dengue) so I have some idea how it works.
Most countries have flu surveillance networks, where they sample from general practitioners swabs and look for new strains. In most cases this works reasonably well.
In Australia we have ASPREN for influenza-like diseases. There are also compulsory notification diseases, but in the pre-COVID days these were mostly useful for things like detecting outbreaks of whooping cough or measles, and weren't really used as flu tracking or detection.
> I also have no idea why people have this notion to reject that COVID-19 may not have originated from China
Because the first large scale outbreak occurred in Wuhan in December 2019. It seems pretty odd that it should have originated in Europe, somehow avoided any outbreaks, travelled to China, then come back to Europe via people who have been traced where it suddenly caused a huge outbreak.
> especially the fact that most of the spread of COVID-19 came from Europe, so much so that Gov. Cuomo actually called it the Europe virus
I presume you and everyone knows why this was - that China locked down quickly and Europe didn't.
Look - I guess the European origin is possible. But it's a pretty out-there theory and it needs some pretty extraordinary evidence (and antibody studies aren't convincing on their own) as well as explanations for the problems outlined above. And there's huge evidence pointing to the China origin theory to overcome too.
Take the genomics - there's a single original strain, which was detected in China, and the mutations clearly come off that. Again -it could be possible that strain was transported there but no where else or something, but it is lots of coincidences here, whereas the China origin story fits everything about how every coronavirus we've ever studied before behaves.