A global pandemic of Biblical proportions is sure to spawn a few new sexually transmitted diseases. Take this Spitter from Left4Dead2 for example. Sure she's easy on the eyes, but did you know that the ball of mutated stomach acid she spat at you actually serves as a carrier for Gack-Throat?
GT effects the central nervous system when the bile makes contact with the genitals. Expect complete paralysis within a matter of hours.