Oh man, i love satrek's werewolf idea.
Or, possibly, there could be a werewolf-lord, or a werewolf monster that acts like lords. That is, he walks all around the island during the nighttime, or at least on one random day a week. He's indestructable, and when he attacks he has a speed of like 7 (only when he attacks though
).
When he attacks you, you don't get killed, but you get turned into a werewolf and you can spread the disease from there. This'd mean that if only one person came across the lord in a night, the disease would be small, but if lots of people got struck by the lord, then there would be a really rampant disease.
That's just a thought though, i like satrek's idea more
