look for antibodies in the blood. are proteins that can fight off infections. CDC is working with state, local, territorial, academic, and commercial partners to better understand COVID-19 in the United States.
CDC has an overarching strategy for learning more about how many people have been infected with SARS-CoV-2, the virus that causes COVID-19, and how it is spreading through the U.S.
population. This strategy includes using serology testing for surveillance to better understand how many infections with SARS-CoV-2 have occurred: Serology tests look for antibodies in blood.
If antibodies are found, that means there has been a previous infection. Antibodies are proteins that can fight off infections.