SAN DIEGO (Sept. 13, 2021) Sailors embarked with the Medical Treatment Facility (MTF) aboard the Military Sealift Command (MSC) hospital ship USNS Mercy (T-AH 19) conduct rapid, COVID-19 antigen testing on the pier during Mercy Exercise (MERCEX) 21-4, Sept. 13, 2021. MERCEX 21-4 is a week-long, pierside training evolution that culminated in a capstone emergency scenario. Mercy can steam to assist anywhere to provide relief as a symbol of Navy Medicine’s abilities around the world, and must be in a five-day-activation status in order to support missions over the horizon, and be ready, reliable and resilient to support mission commanders. (U.S. Navy photo by Mass Communication Specialist 2nd Class Jake Greenberg)