This is Getting By by Shakes Peer2B.
The terrorists finally got a bio-weapon and released it in Western countries. They didn't count on it spreading so fast or killing so effectively. When the dust settles there is only a very small percentage of the human population remaining. This is the story of one group, led by Gavin Thompson, on a mission to resurrect humanity. This story begins the 'Post-Sickness' saga. Read it first.
This is the sequel:
Getting Ahead by Shakes Peer2B.
It's only four years after Gavin Thompson's disappearance, but around the fringes of the new nation of Phoenicia, trouble is brewing. Useful pre-sickness artifacts are becoming rare, and the scavs and barbs are banding together to see if they can't take some of what Phoenicia has. The President's sister, Sophie Chen-Thompson makes it her personal mission to see that no other little girls have to wait for fathers who aren't coming home... Read 'Getting By' before you read this.