Dark matter trilogy

A deadly, mysterious epidemic is sweeping the country, and young kidnap victim Callie is one of the few who survived infection, only to be sacrificed by her captors at a secret lab working with antimatter; her older brother Kai is desperate to find out what happened to her--his best hope lies with Shay, the girl who last saw Callie alive, and together they will seek answers, even if it means evading soldiers and crossing the quarantine zone.