Stargate Search

I'm looking for an apocafic, where there's an outbreak of flu, that was brought over from offworld. They manage to get it under control, with help from the Asgard, but one of the scientists they brought in to help them took a sample with him to manipulate for biological warfare. The lab has an accident and the now even more dangerous flu strain gets out. One of the guards runs at the warning and spreads the sickness to others. The SGC starts the evacuation to the Alpha site. President Hayes changed the position of Homeworld Security to a Cabinet Post, so Jack is the 16th in succession for the role of President. He orders Jack to stay on the Daedalus, which is in orbit around earth.
About 96 or 98% of the earth population dies. They figure out what the flu strain was and change the vaccine they'd made for the original strain.
Meanwhile, people are having strange dreams. Either they're of a nice old woman, telling them to come to her (can't quite remember where). Or they're of a dark man, who's telling people to come to Vegas. It turns out that it's time for a new confrontation between good an evil. They both choose a champion. She sends off several men. For the evil side it's Ba'al. Last time this confrontation took place the good lost and thus the Goa'uld reigned. She comments that Hayes chose well, when making Jack one of his successors. Jack's the President, since everyone else in the line died from the flu.
The SCG-people are unable to help the Chosen One directly, but watch over him from in the Daedalus. When one of the guys that sided with evil sets off a naquada-enhanced bomb/missile, Vegas is destroyed along with the evil guys. The people on the Deadalus beamed up those of the Chosen, that they could. I think there was one of them that they couldn't get a lock on though.
I think that it's in this story, that Jack decides to send several ships and navy crews to Atlantis, because it's surrounded by water.

That's pretty much all I can remember. I think that it might be a crossover, since I remember seeing the thing with the Chosen elsewhere as well, but I'm not sure.

Thanks in advance.

Found: Earth Abides by Texan