The "cryptohantavirus" was made up, but there are hanta viruses, monitored by the CDC, that are transmitted by rodents and cause pulmonary death.
The "Zitek" building in this episode was also used in an episode of the X-Files in 2000 as the "FPS headquarters"; season 7 episode 13. The word "Zitek" is added to the front of the building and the first two numbers (2 and 5) of the address removed from the building leaving just a 3 and a 4.
Red-haired actress: Amy Price-Francis.