The Iratus bug retrovirus is a form of gene therapy developed by the Atlantis expedition under the supervision of Dr. Carson Beckett. Devised as a means of combating the Wraith, the retrovirus is capable of essentially transforming a Wraith into a human for a limited period of time.
During the first year on Atlantis, the expedition team discovered that the Wraith were created when human genetic material became mixed with that of the Iratus bug. Dr. Carson Beckett was convinced that this process could be reversed, leading to an effort to devise a treatment that would remove the Iratus bug DNA, leaving the subject entirely human. (SGA: "The Gift")
The retrovirus was first used by a young female Wraith named Ellia, though without Beckett's knowledge or permission; believing the retrovirus not to be ready for a clinical trial, a fear that proved justified. Ellia began to transform into a creature still closer to the Iratus bug — much the reverse of the retrovirus' desired effect. She became violently hostile, and was eventually killed by Lt. Colonel John Sheppard and Ronon Dex. Sheppard was also infected with this version of the retrovirus, and began to mutate in a similar way. Beckett was able to reverse the process using Iratus bug stem cells as a base for a new retroviral treatment, successfully reversing the mutation in Sheppard. (SGA: "Instinct", "Conversion")
When Beckett did complete a trial version of the retrovirus, it was tested in more controlled conditions on a Wraith that Sheppard dubbed "Mike." Over the course of several days, the Wraith did indeed assume a fully human appearance, along with suffering near-total memory loss. He was eventually told that his name was Michael Kenmore, a human member of the expedition, and allowed to move, escorted, around the city. However, Michael did exhibited latent memories of his time as a Wraith, and his physiology did not become entirely human; he required periodic injections to prevent his Wraith DNA from reasserting itself. Most notably, he appeared to retain heightened senses and a degree of the Wraith's physical and psychic abilities. Michael also responded very negatively upon learning the truth of his identity, eventually escaping and making his way back to the Wraith. He may not have completely reverted to his original Wraith form, however; other Wraith at least could easily sense that he had been affected by the retrovirus. (SGA: "Michael", "No Man's Land", "Vengeance")
Work continued on weaponizing the retrovirus as well, with Beckett and Dr. Radek Zelenka developing a means to disperse it in aerosol form. This version of the retrovirus was tested in cooperation with a Wraith Hive ship that Michael had brought to Atlantis, seeking an alliance; it managed to transform a Wraith into a human in a matter of hours. It also proved to be effective en masse, as the crew of the Daedalus discovered after finding itself in battle with the Hive; the retrovirus was dispersed through the Hive's ventilation system, successfully converting all the Wraith except for the Queen. Once again, however, the retrovirus proved effective for only a limited amount of time, requiring periodic follow-up injections. And several of the converted Wraith's memories began to return even while they were nominally human. (SGA: "Allies", "No Man's Land", "Misbegotten")
It is unknown whether the retrovirus has been further refined since this incident by the Atlantis expedition. Michael, however, developed a similar technique to create a hybrid creature based even more strongly on the Iratus bug than the one Ellia and Sheppard had nearly mutated into. (SGA: "Vengeance")
The expedition soon was able to use a more modified version of the retrovirus to return the Athosian Human-Wraith Hybrids back to normal. It is unknown if the effects will reverse themselves. (SGA: "The Seed")