Broken Souls (The Chronicles of Mara Lantern, Book 2)

In the alternate reality from which Juaquin Prado hails, when a person dies, his spirit is interred, not his body. So when Prado gets killed during a botched bank robbery, his soul, left unattended, goes viral, possessing dozens of people simultaneously, evicting them from their bodies and causing them to decompose even though they are still alive.

As if Mara Lantern doesn’t have enough to worry about. Now, in addition to mastering her new metaphysical powers and having a mentor with a propensity for turning into a dragon, she must deal with mindless rotting people roaming the streets of Portland, Oregon.