Pathogenesis is a deck-building game where players are bacterial pathogens attacking a human host. Pathogenesis STD adds the fourth tract to the body, the Genitourinary tract, introducing pathogens, traits, and virulence factors appropriate for this area of the body. Further, keeping to the science, the Genitourinary tract has no toxin cards but instead a new mechanic has been introduced, Collateral Damage cards! (Base game required to play).