Had something really weird happen to me just now.
An Alpaca farm field got illness and then it jumped to residential houses far away.
This "diseased" field I could demolish even with illness on it, and I also tested putting a hospital next to the field and a doctor went to the field to "cure" it, after which I got the usual message saying "Your people are healthy again".
Well I guess Alpaca's are people too now...
Another modder also told me: "The field modules have an IncidentInfectable container which enables disease and fire on them. Don't ask why, but it is there."
Is this supposed to be a joke? (If so, I'll try to go along with it and call this the Alpaca Covid)
Here is the savegame in case you need it:
https://drive.google.com/file/d/15BXBfkeikfO6tBAnmzmy5hVQu9AzH8gZ/view?usp=share_link