PHOTOS: Maricopa County wants to know how many people have actually had COVID-19, beyond those confirmed with a test.
And they may be knocking on your door to find out.
The Maricopa County Department of Public Health is launching an antibody study in partnership with Arizona State University and Mayo Clinic to estimate actual infection rates and possible immunity.
If you live in one of 29 chosen neighborhoods, you may get a knock on your door in mid-September asking for your voluntary participation in a free antibody test.
The testing project, called a "serosurvey," involves collecting blood samples from a representative population of county residents. The blood tests will search for COVID-19 antibodies, which are disease-specific blood proteins built during an immune response to fight an infection.