Phage

The anti-Wraith pathogen phage was a virus developed by Carson Beckett's clone.

When a person is infected by the Wraith pathogen, it lies dormant for a while and then parasitizes the body, immobilizing it, growing many tendrils and taking over part of the brain to use for its own consciousness. The tendrils extend in all directions and seek out sources of energy to accelerate its growth. Given enough time and power, it will eventually grow into a Wraith hive ship.

A genetically engineered virus can be injected into the host body to kill the pathogen while leaving the host alive. This virus does not destroy the tendrils themselves, but it renders them lifeless and inert.

History
After Dr. Jennifer Keller was infected by the pathogen, the cloned Dr. Carson Beckett developed the phage and tested it on John Sheppard, who, like most of AR-1, was also infected by the pathogen but not showing any symptoms yet. It successfully cured him. Ronon Dex volunteered to go into the pathogen-covered isolation area and inject Keller with the virus because he was also infected and the pathogen would recognize its own DNA inside him and let him pass. This worked until he was forced to fire, making the tendrils choke him almost to death. Sheppard then crashed a Gateship into the tower where Keller was being held, and managed to inject her. The tendrils attacked him and he was about to kill Keller when the pathogen died. Without the organism infecting her, Keller returned to normal.