Diseases may be acquired in one of the following ways:

• Airborne: The toxin is in the air. If a character is aware of the toxin he can hold his breath for a number of rounds equal to 2 plus his Vigor die, or half that if he wasn’t prepared. After that he must breathe and automatically contracts the disease. If the victim is surprised by the release of the disease (such as a creature with exploding spores), he must make a Smarts roll to hold his breath before the tainted air enters his lungs.
• Touch: The victim must make a Vigor roll immediately on being touched. If successful, the disease didn’t manage to “take” and there is no effect. Failure means the disease takes immediate effect as described below.
• Induction: The disease must enter the bloodstream, most typically by an animal's bite, or a cut by an infected weapon. In these cases, if a victim is Shaken or wounded by such an attack, he must make a Vigor roll. If failed, he contracts the disease. If successful, the disease didn't manage to get into the bloodstream and there is no further effect.

Savage Worlds Deluxe Edition p. 100