An incurable degenerative disease affecting Vulcans, Romulans and Rigelians, which Julian Bashir discovers in the Tal Shiar chairman Koval during a conference on Romulus.
Tuvan Syndrome appears in the Deep Space Nine episode Inter Arma Enim Silent Leges. Sufferers gradually lose motor control over a period of years and most die within about two decades of the first symptoms.
Bashir travels to Romulus for a medical conference, and Koval, head of the Tal Shiar, questions him closely about the Dominion's morphogenic virus. Sloan of Section 31 asks Bashir to confirm a rumour that Koval has the syndrome, and the doctor sees signs of it.
Bashir comes to fear that Section 31 means to speed the disease along and kill Koval. The supposed plot is a deception: Koval is secretly Section 31's own source inside the Tal Shiar, and the affair is staged to discredit Senator Cretak.