Souls of fire, book 1: Fireborn
Keri Arthur2014

Sam is working undercover for the Paranormal Investigations Team, and those who are trying to murder him are actually humans infected by a plaguelike virus, the Crimson Death - a by-product of a failed government experioment to identify the enzymes that make the vampires immortal. Now all those infected must be eliminated.

But when Emberly's boss is muredered and his ireeplaceable research stolen, she needs to find the guilty party before she goes down in flames.