U.S. Air Force Airmen receive a briefing on how to swab their mouths at a COVID-19 test site on Joint Base Langley-Eustis, Virginia, Oct. 7, 2020. The 633rd Medical Group is piloting a new process known as Sentinel Surveillance testing, which provides the capability to identify any undiagnosed prevalence of COVID-19 in asymptomatic base populations. (U.S. Air Force photo by Staff Sgt. Delaney Gonzales)