Siddhartha Mukherjee:

Well, there are several things we have learned.

First of all, we have learned that a that the virus is mainly transmitted through respiratory droplets or so-called fomites. That's the main mode of transmission.

The second thing that we have learned, or trying to learn, we're in the middle of learning, is that there are several people who are asymptomatic who may be shedding virus. That's a very, very important idea. That is to say that there may be a child or someone who doesn't have any symptoms, no fever, no diarrhea, no respiratory symptoms, but nonetheless is shedding the virus.

We need to identify those people and isolate and potentially quarantine them, so that they don't keep spreading the virus.

The third thing that we are learning, which we haven't learned for sure, is that there seems to be if you do the right kind of test, there seems to be a way to predict whether you're going to have very severe disease vs. a more mild form of the disease.

And that helps because that will help us triage patient to those who are either going to be sick and therefore require urgent attention vs. those who may become less sick and may be able to be managed more conservatively too.

Continued here:

What scientists know about COVID-19 -- and what they don't - PBS NewsHour