The only recent evidence it contains is the fact that 3 researchers from WIV sought hospital care back in autumn of 2019 with symptoms similar to COVID. However, this piece of evidence is hardly consequential without further details:
- First, most common symptoms of COVID are indistinguishable from common cold. If the researchers were known to have any "signature" symptoms like loss of smell the article would certainly mention it.
- Second and more importantly, China doesn't have a robust GP/family doctor system found in western countries. As a result, many people would go to hospitals directly whenever they're mildly sick.
Taking the evidence as we know it now, the straightforward explanation is that 3 researchers caught cold, got mildly sick, so went to the hospital to get prescriptions or doctor's notes for sick leave (in China it's common for employers to require a doctor's note even for a short sick leave).
That said, I believe the lab leak theory is still plausible, and shouldn't be ruled out unless a clear transmission path from bat to human has been identified (which was done for the 2002 SARS outbreak). But I also think that we may never know. I trust that some theories put forward were in good faith, but so far they are little more than speculations.
The sudden shift is just baffling to me though. This huge new furor is due to anonymous CIA sources saying three people got sick? That's extremely tenuous evidence, as you state above.
As far as I can tell, the only biological evidence is the furin cleavage site, which is not uncommon in related viruses. Also, this has been known since the beginning, when the Chinese CDC released the first genome of the virus.
This seems more like people declaring victory because they're finally getting a hint of public support for their suspicions, rather than some truly damning evidence.
I don't have strong views as it's incredibly difficult to prove a negative (that it was not a leak), essentially you would have to identify and prove exactly the actual vector and even then it might be difficult to be conclusive. Lab leak seems however like a very likely scenario and it is crazy how people try to dismiss it without any actual evidence either way - and China's approach to handling the investigation and information flow definitely should cause anyone to be suspicious.
I guess at this stage thr only way we cam find out is if in 10-20 years there's a whistleblower from the lab.