Bloodstream by Tess Gerritsen:

In Bloodstream, Dr. Claire Elliot relocates with her teenage son to the small town of Tranquility, Maine, hoping for a fresh start. But when local teens begin exhibiting violent, psychotic behavior, she realizes something far more sinister is happening. As she searches for the cause, Claire uncovers a terrifying link buried deep in the town’s past—and someone will do anything to keep it hidden.

Tess Gerritsen crafts a gripping medical thriller blending suspense, science, and human fear in a chilling story that asks: what happens when the cure becomes the cause?