Genetic virus

From Memory Alpha, the free Star Trek reference.

The genetic virus was a deadly virus used by The Albino to kill Kang's son, Dax as well as the sons of Kor and Koloth. This lead these Klingons and Curzon Dax the namesake of Kang's son to swear a blood oath to cut out the Albino's heart. (DS9: "Blood Oath")