A study led by the National Institutes of Health, the University of Alabama at Birmingham and the University of Pittsburgh will examine how many adults in the United States have been infected by the novel coronavirus but did not know they had it. Researchers will analyze blood samples from 10,000 adults from across the USA to see if they have the antibodies to the virus, which indicates a prior infection.

Each participant, after confirming they have not been diagnosed with COVID-19, are healthy and do not have any symptoms, will be sent a test kit that contains a finger stick to provide a blood sample. The sample will be sent back to the NIH, where it will be processed to find out if that individual has antibodies to SARS-CoV-2.

The results will demonstrate where the novel coronavirus has spread undetected in the United States and provide insights into the types of populations that are most affected.

The data from the study will also help researchers understand herd immunity.

"Absent a vaccine, we want to reach herd immunity," said Robert Kimberly, MD, the study's principal investigator and the director of the Center for Clinical and Translational Science at UAB. "For most diseases, 50 percent of the population needs to have been exposed. But with the infection rate of COVID-19, 65 to 70 percent of the population needs to be exposed to build up herd immunity.