Invasion - Robin Cook

New York Times bestselling author Robin Cook's "pressure cooker of a thriller" (Booklist) takes medical technology into a new realm, where everything we know about the human body—and the universe we live in—is about to be challenged.
Everyone assumes it's just the flu—but when a powerful virus causes unexplained symptoms, the few left uninfected must discover a cure before they catch it, too...
After Cassy Winthrope's boyfriend Beau displays brief, flu-like symptoms, he begins to act strangely. His body is stronger and faster, his mind shaprer. And suddenly the straight-edged guy who never skips class and hates big dogs is playing hooky and walking around with a bullmastiff.
Once Cassy shares these observations with their mutual friend Pitt, the pair notice that almost everyone else in their small college town seems to be infected with the same virus that Beau has. Could it be connected to the tiny black disks appearing everywhere, stinging those who pick them up?
Recruiting members of the community and medical experts unexposed to the disease that's defying all diagnoses, Cassy knows she's in a race against time. But can she figure out how to save the people she cares for—before it's too late to reverse the changes?