An anonymous reader quotes Wired: Next week, blood banks across the Netherlands are set to begin a nationwide experiment. As donations arrive — about 7,000 of them per week is the norm — they’ll be screened with the usual battery of tests that keep the blood supply safe, plus one more: a test for antibodies to SARS-CoV-2, the virus that causes Covid-19. Then, in a few weeks, another batch of samples will get the same test. And after that, depending on the numbers, there could be further rounds. The blood donors should be fairly representative of Dutch adults ages 18 to 75, and most importantly, they’ll all be healthy enough for blood donation — or at least outwardly so… Identifying what proportion of the population has already been infected is key to making the right decisions about containment… [B]ecause no Covid-19-specific serological [antibody] tests have been fully vetted yet, the FDA’s latest guidance is that they shouldn’t be relied upon for diagnoses. But in epidemiology circles, those tests are a sought-after tool for understanding the scope of the disease. Since February — which was either three weeks or a lifetime ago — epidemiologists have been trying to get the full scope of the number of infections here in the U.S… [A]s the disease has continued to spread and a patchwork of local “stay at home” rules begins to bend the course of the disease, projecting who has the disease and where the hot spots are has become more difficult for models to capture. Instead, you need boots-on-the-ground surveillance. In other words, to fill the gap created by a lack of diagnostic tests, you need more testing — but of a different sort. This time you have to know how many total people have already fought the bug, and how recently they’ve fought it. “Of all the data out there, if there was a good serological assay that was very specific about individuating recent cases, that would be the best data we could have,” says Alex Perkins, an epidemiologist at the University of Notre Dame. The key, he says, is drawing blood from a representative sample that would show the true scope of unobserved infections… Another motivation to develop better blood tests is the potential to develop therapeutics from antibody-rich blood serum. Wired is currently providing free access to stories about the coronavirus. Read more of this story at Slashdot.