[3.5] Contagion Plague

[Segial]

In a political campaign of mine, the characters are the leaders of a small nation that has to deal with a large scale harpy infection. One of my players asked me if he could start an epidemic using the contagion spell. Would a character infected by a sickness from the contagion spell be able to spread the disease, and what would be the rules for it?

[Seffbasilisk]

Yes, and the details for disease are spelled out in the DMG IIRC.

Disease

When a character is injured by a contaminated attack, touches an item smeared with diseased matter, or consumes disease-tainted food or drink, he must make an immediate Fortitude saving throw. If he succeeds, the disease has no effect—his immune system fought off the infection. If he fails, he takes damage after an incubation period. Once per day afterward, he must make a successful Fortitude saving throw to avoid repeated damage. Two successful saving throws in a row indicate that he has fought off the disease and recovers, taking no more damage.

These Fortitude saving throws can be rolled secretly so that the player doesn’t know whether the disease has taken hold.