Xenovirus Prime was a genetically engineered virus designed by Doctor Fizz Galko who served as a bioengineer for the Sith Empire. This was considered amongst his greatest experiment with the intention of introducing a pathogen that targeted alien species who were loyal to the Galactic Republic. Those carriers of the virus posed no risk of infecting others.
During the Cold War, the virus was used as part of an initiative against the Republic and was being used on Belsavis. Doctor Galko was responsible for administering the virus to the planet's most dangerous prisoners who were the intended carriers and vectors for spreading it to the Republic. He would later task a Sith spacer with detecting the infected aliens and marking their cells for Imperial reference.
- Star Wars: The Old Republic (First appearance)