Honestly, stopping plagues can be a real hassle. Causing them isn't so hard, but stopping them can be a hassle. Unless the population isn't that large you're unlikely to make a dent in things with just that. Some other measures would be in order really.

But forgive me as I'm not a Pathfinder fan so I'm not familiar with the adventure. So I have a few questions.
What's the city's population?
What level and classes are your party's spellcasters?
What kind of funds do you have to use to resolve this issue?
Do you have access to DnD 3.5 material or just Pathfinder?