Once Upon a Time in Wonderland (2013)

S3E13 Fever

After a scientist is killed, a lab rat manages to escape during a botched case of industrial espionage. The situation escalates when the rat, carrying a newly developed virus meant to fight HIV, becomes Screed's dinner. This virus turns deadly for vampires, growing stronger every time they feed. As it swiftly infects the vampire community, Vachon, Nick, and LaCroix fall victim to it. With the clock ticking, Nick frantically searches for the murderer while Natalie works tirelessly to develop an antidote.