Soldier Protector by Kimberly Van Meter

Their mission? Save the world - and each other!

Dr Caitlin Willows must create a cure for a terrifying new biological weapon. Zak Ramsey's assignment? Keep her alive long enough to do it. As part of an elite squad, he knows how to respond to deadly threats, but nothing prepares him for falling for Caitlin. They might hold the fate of humanity in their hands, but controlling their desires is the more difficult task...