Correctional and detention facilities are disproportionately burdened by the COVID-19 pandemic. Early detection and proper care for persons with SARS-Cov-2 is essential to slow transmission within these facilities. This study conducted in partnership with the Louisiana Department of Health and CDC, evaluated the effectiveness of serial testing to identify people with SARS-CoV-2 infection. This MMWR report investigated the serial laboratory testing following a staff member in a facility in Louisiana who developed symptoms on March 29, 2020. Two additional staff members tested positive in early April, and the first case in an incarcerated person was detected on April 7. From May 7-21, 98 incarcerated and detained people were tested for SARS-CoV-2, of which 71 tested positive.