Antibodies are an immune response to infection, and the presence of them suggests the person was infected with the virus whether they showed symptoms or not. Antibody testing for the disease does not detect active cases. But antibody tests are a critical tool to show how the disease spread through the population.
Antibody testing differs from diagnostic testing, which tries to determine active cases. Diagnostic testing has been limited in Georgia and most states, and many who likely had the disease over the past several weeks have not been tested.