Parishes occasionally get infected with the plague. When this happens you must send monks with restoration to cure the plague. The longer the plague is left the worse it gets meaning it will take much more monks and faith pints to cure so its best to cure it early because if it becomes too big it can be very hard to cure it yourself.
Try to leave the plague in enemy parishes to hinder your enemies growth.
The plague gives negative popularity to all the villages in the parish.
If the plague gets too big in a parish it will spread to nearby parishes in the form of a diseased rat that will travel from the infected parish capital to another parish capital infecting it.
When the level of plague in a parish reaches 30 points, diseased rats will start to spread to other parishes nearby.
The highest a plague can go in a parish is 200 points
These rats can be seen travelling across the map