Each turn in Virus! you either play a card or discard any number of cards, then you replenish your hand to three cards. Cards can be:
- One of four organs (or the joker organ)
- One of four viruses (specific to each organ or the joker virus)
- One of four pills (specific to each organ or the joker pill)
- A special action card
You can play only one of each organs in your player area. Pills and viruses can be played on any player's organs, but only on the same color organ. A second pill on any organ immunizes it against infection. Your goal is to be the first to have four healthy organs in front of you.