So my limited understanding is that during the 5-14 day incubation period, some people's bodies are able to fight the virus before it takes hold and causes symptoms. That's how they have antibodies but no symptoms. Remember, symptoms (fever, cough) are often your body's reaction to the virus, not caused by the virus itself.
I understand this, and this certainly makes containing the virus nearly impossible.
However, my understanding is that a large percentage of people are never getting sick from the virus. That shouldn't be possible. Unless it's a combination of variables or other factors. Unless someone can find some papers about other dangerous viruses causing no symptoms at all in some people. I know you can have carriers but they usually at least get sick, especially for more virulent diseases.