Adril Sark was a joined Trill, a host of the Sark symbiont. Adril Sark was an epidemiologist and consulted with Starfleet Medical and the Federation Medical Association on the analysis of samples of the Teplan blight gathered by Lieutenant Dr. Julian Bashir on the Teplan homeworld Yarmta in the 2370s. During the Dominion War Adril was part of a team attempting to develop a virus targeting the Jem'Hadar genome for use as a biogenic weapon. The weapon was never tested due to Federation President Min Zife's ethical concerns, though as far as the later host Tyria Sark was aware, the project was never cancelled. (The War of the Masters: "A Good Compromise")