I just was notified that somebody not in my party and unknown to me has contracted plague. The "Jump to location" button is grayed out. None of my colonists is sick. I am running the Prepare carefully mod, nothing else.
The same bug happened to me as well. Same version, only I don't have any mods running.
Thirding this, last time it happened was Xorkun, engineer who doesn't exist in my colony. Happened 3 times so far (maybe same name?), playing cass rough in jungle.