Alpha Infected by Christa Tomlinson

Wolf shifters Captain Ice Anderson and Corporal Hazard Mitchell have been happily mated for a year. But as members of the elite special forces team the 448, their lives are still filled with action and danger. And now their pack has been tasked with its most dangerous mission yet.
When a zombie outbreak sweeps through the city, the 448 are sent out among the horde to retrieve the antidote that can stop the spread of the virus. They embark on the perilous mission, knowing that failure will lead to the deaths of thousands of people. The operation goes well… until the unthinkable happens.
Now the team is in a race against the clock and the stakes for obtaining the cure are even higher. Will Ice and Hazard come out of this mission alive and together or is their fated love destined to be tragically short lived?

Alpha Infected is a sequel novella to Alpha Awakened. It can be read as a standalone, but your experience with the pack will be richer if you read Alpha Awakened first.