The Virus Expansion expands the base game for Cytosis. The expansion introduces Influenza, Rhino Virus and Ebola. Players can pay ATP to build up their antibodies to each of the three viral strains. When a Virus attacks, all players roll a number of antibody dice according to their level of health and add it to the antibodies they've accumulated throughout the game. The player with the highest antibody response will gain resources while the player with weakest antibody response loses resources.