Following the events on Volia, the Aschen started dialing the list of Stargate addresses given to them by Colonel Jack O'Neill in their plan for galactic conquest. The first planet they dialed was being consumed by a black hole and as a result, Mollem and several of the Aschen leaders were killed. In retaliation, the Aschen tasked scientist Mirris, who was also Mollem's wife, to come up with a bioweapon to wipe out the Tau'ri.
Mirris was eventually able to create a smart bioweapon with 98% efficiency and made a deal with Ryn of the Pack for him to use the pretext of a treaty with the Tau'ri to infect them with the bioweapon. Ryn was successfully able to pass the bioweapon off to the Tau'ri in the form of a flower from the Pack ship Wanderer which didn't activate until it was exposed to Earth's biosphere. The virus infected the personnel of the SGC, but remained quietly dormant in their bodies, spreading to the SGC personnel's families and everyone they came into contact with. Finally, after a couple of months, the virus went active, causing instant sterility in those afflicted by it of both sexes and terminating all active pregnancies. By the time the virus went active, it was global and affected people worldwide. However, Mirris was sloppy in creating the virus and it mutated and jumped species to infect plants and animals as well, all except a few species of bird that were naturally immune and cockroaches. The effects of the virus caused chaos on Earth with governments collapsing, people turning against each other and eventually those that could escape off-planet fleeing to places such as Chulak and Holdfast. The Earth was eventually turned into a barren wasteland with the only life being the immune bird species and cockroaches with not even trees surviving.
The effects of the virus went interstellar, presumably through infected SGC personnel on missions before the virus went active. Thousands of worlds suffered the same fate as Earth and the rest of the galaxy started to be decimated in a war between the Goa'uld System Lord Anubis and the Replicators. The survivors of the Tau'ri then began waging a guerilla war against the Ashen, led by Commander-in-Chief Jack O'Neill. To fight back, the Tau'ri scavenged weapons and got biological modifications and began using nanites in combat. They also made an ally out of at least one Reetou, Ite-kh who joined their war effort. However, while the Tau'ri were able to win a few victories, the virus, which eventually burnt out, had already done too much damage to the Tau'ri who faced extinction within a generation with all of the other planets affected by the virus facing the same fate.
Eventually, Tau'ri forces discovered a lab belonging to the Ancient Janus containing a series of time travel devices. Seeing the devices as their only hope, the Tau'ri forces began a series of temporal incursions into the past in an attempt to change history and prevent the war from occurring. The Tau'ri forces made ten incursions, some to make a change and others to reverse changes that ended up making things worse usually involving Vice President Robert Kinsey. One such attempt featured the future Tau'ri attempting to strike at Mirris first and Kinsey's intervention causing an interstellar war.
With one final trip available to them, Commander O'Neill, Ite-kh and O'Neill's daughter Jade attempted to disrupt the Pack-Tau'ri treaty that started off the war to the point of O'Neill being willing to use a naquadria-fusion bomb to nuke the summit on Kytos to change the future and get revenge for all of those lost. Jade was captured by the 2003 version of her father and showed him the truth. Unwilling to kill so many people, Jade aided in disarming her father's bomb, but both O'Neills were captured by Mirris who launched an attack on the Pack with her Aschen warship, destroying many Pack vessels and infecting the Wanderer with a biogenic weapon. Using Janus' time travel devices as a teleport, both O'Neills, Jade and Doctor Daniel Jackson used the naquadria-fusion bomb to destroy Mirris' ship, with Mirris being killed by the future O'Neill during the operation.
Following the defeat of the Ashen at Kytos, the plant that was going to be used to spread the virus was identified and destroyed, preventing its release on Earth and altering the future in which the war had occurred. Ryn was also exposed after killing Ite-kh and was killed himself by Teal'c. Due to the damage the Pack took, they were forced to find a planet to settle on for the first time in millennia while Jade and the future Jack O'Neill decide to return to the future despite the fact that due to their timeline no longer existing, they could be erased. Before leaving, Jade destroyed all of their future technology and disabled the Stargate on the planet where they found Janus' lab so that no one else could ever find and use Janus' time travel technology. (SG1: "Relativity")