I'm a bit confused reading articles like this: https://www.nytimes.com/2020/04/23/nyregion/coronavirus-antibodies-test-ny.html
One of every five New York City residents tested positive for antibodies to the coronavirus, according to preliminary results described by Gov. Andrew M. Cuomo on Thursday that suggested that the virus had spread far more widely than known.
If the pattern holds, the results from random testing of 3,000 people raised the tantalizing prospect that many New Yorkers — as many as 2.7 million, the governor said — who never knew they had been infected had already encountered the virus, and survived. Mr. Cuomo also said that such wide infection might mean that the death rate was far lower than believed.
As per this previous Stackexchange question, it appears that we have no way of knowing whether someone has coronavirus antibodies or not. So I have a few follow-up questions:
- How do they detect whether someone has coronavirus antibodies?
- Does someone having the antibodies mean they were definitely infected with the novel coronavirus at some point?