US begins blood tests for coronavirus immunity: reports

The United States has begun taking blood samples from across the country to determine the true number of people infected with the coronavirus, using a test that works retrospectively, according to reports.The new tests are based on serological surveys, which differ from the nasal swabs used to determine if someone currently has the virus.Instead, they look for whether certain antibodies are present in the blood which shows that the person fought and then recovered from the illness -- even if the