Walter Skinner was infested by this, and Alex Krycek was able to inflict a great amount of pain to him. The exact origins of the nanovirus are unknown, but Krycek was able to command them using a type of touch-pad remote control he manipulated as necessary. Apparently there were levels of this virus and Skinner actually died briefly but Krycek reduced the level of intensity of the virus and Skinner come back to life. Krycek used this to threaten Skinner.S.R. 819