As the nation looks for ways to emerge from the shelter-in-place orders instituted across the country, there's growing hope that our blood might hold clues for how we move forward.Late last week, the National Institutes of Health (NIH) announced that it has begun recruiting volunteers for a study to determine how many Americans without a confirmed COVID-19 diagnosis have been exposed to the SARS-CoV-2 virus, based on the presence of antibodies in their blood.This "serosurvey" will analyze blood samples from more than 10,000 volunteers for the presence of two antibodies, immunoglobulin M (IgM) and immunoglobulin G (IgG), that the body produces in response to a virus.