Chasing Secrets by Gennifer Choldenko

 Thirteen-year-old Lizzie Kennedy has a passion for science, but there's not much opportunity for her to pursue it at the exclusive girls' school she is forced to attend in San Francisco in 1900. While on a trip to a patient's house with her physician father, Lizzie observes evidence that the much-feared plague has made its way to their beloved city—despite the fact that everyone, even her own father, denies its arrival. With the help of Noah, the son of their Chinese cook, Lizzie investigates this disturbing discovery that could spell death for many.  (Booklist)