You are conflating a test for active virus versus an antibody test. my suspicion is that a very large percentage of people in certain neighborhoods of New York City are going to show up having been exposed and never presented symptoms. I just don't compute how else you can explain this with a virus that is so transmissible. we should also keep in mind that the number of deaths isn't necessarily indicative by itself of number of infections since deaths can be caused by hospitals being overrun.