I'm sure very little and that's not a criticism. Medical science is still probably in it's infancy. For everything we know about the human body, there are a hundred things we don't know. For every disease we have a cure for (which is very few) there are a hundred we don't. For everything we know the cause of there are a hundred conditions we don't. Today's world literature in medicine will be revised tomorrow. As to all the thousands of viruses, what we know could be kept in a thimble.
I'm not in any way putting down your profession or research. It's necessary and we learn something new every day. We figure out treatments every day, but then something else pops up. When it comes to viruses like this one I would call the expertise in the subject mostly just educated opinions, but not absolute scientific proof. I do caution anytime scientists think they've solved secrets, that science was long convinced the earth was flat.
Then that's what makes medical research exciting to some, to know there are an infinite number of things to study and learn.
Not that many years ago we didn't treat viruses. Now we've learned the dangers but we also now have antiviral drugs for some of them. We know so much, but compared to what we don't know, we know so little. I think I'm being generous in saying we've learned about 10% of what there is to learn. I'm very thankful for that, but I also accept that even some of the things we think we know, we'll turn out wrong on. Now, I do look toward those in the field and toward research and medical literature for my answers as you suggest and don't take the word on the street. Even then though I put them in context and say, "The current medical consensus is...."