Sci-Fi Book Group: Terminal Alliance, by Jim C. Hines
A plague has killed most of humankind and turned the survivors into feral monsters – all except Lt. Marion "Mops" Adamopoulos and her Hygiene and Sanitation Team. In this humorous military sci-fi tale, the future of humanity depends on a group of janitors, who must commandeer a damaged spaceship and work with an alien species called the Krakau to thwart the villains who are trying to undo the cure for the plague.