Researchers surprised: 20% of Chicagoans in blood-test study came up positive for coronavirus antibodies

Nearly 1 in 5 Chicago residents who sent blood-spot samples to Northwestern University researchers tested positive for antibodies to the coronavirus that causes COVID-19, according to preliminary results of an ongoing study. That 20% infection rate is higher than the scientists anticipated based on earlier research, said Dr. Elizabeth McNally, director of the Center for Genetic Medicine at the Northwestern University Feinberg School of Medicine. One study by other Northwestern researchers tested hospital workers from across the Chicago region and found antibodies in less than 5%.