There's no particular reason to think it's biological warfare. It could be, obviously, but "could be" isn't good enough.
It might have escaped from a lab. That seems more plausible than biological warfare. Labs do investigate viruses and accidents do happen.
Honestly, though, it's not that dissimilar to other viruses. We know about corona viruses. We've seen SARS viruses before. In fact, we've seen SARS viruses that appeared to originate in China before. This all seems relatively normal.
Finally, so what? I'm sure there are people working to find out whether the virus is natural or man-made, but when it comes to producing and distributing a vaccine and slowing the spread of the virus and all the usual pandemic stuff, it doesn't really matter if it appeared naturally in China or was engineered by Martians. Our medical response is the same. IF (and it's a big if) it turns out that this was a bio-engineered Chinese terror weapon then at some point in the future the political hammer can come down, but at this stage it hardly matters.