Omega Virus: Gamma Hour (book 2)
After surviving months in the ZPoc all alone, Tiffany Gainsborough still wanders in search of signs of life. In desperation she leaves radio messages, trying to find Zach, her friends, or anyone at all.
When she comes across a broadcast between two people calling each other Brother and Sister, she is overjoyed... that is until she realizes there's something wrong with them; something very wrong. To make matters worse she hears howling in the distance when she hasn't seen an animal since the Apocalypse began; and the animals, or whatever they are, sound hungry.
The virus has evolved.