Dogma Virus

The Dogma Virus was a virus created by the Free Time organisation.

The virus infects Time Lords, but lies dormant until regeneration, at which point the infected Time Lord is "zombified".

The virus broke out on Gallifrey (BFA: Gallifrey); and at the end of the series, Romana is faced with the choice of letting Gallifrey fall to the virus in the hope of rebuilding it with the Biodata Archive, or administer the "cure" (which would in fact render the Time Lords unable to regenerate).