Human beings are at the edge of existence — but they don't know it yet! Mother nature is about to strike back and reduce mankind to save the planet from being destroyed by the species that calls itself "homo sapiens".
In Viroid, players cooperate in taking the role of a virus and trying to infect people all over the world. They use events like the Olympic Games to spread their deadly effects. To be a step ahead of the human scientists, the players develop special features like infection by blood, infection via animals, or resistance against medicine, heat or cold.
The game is played in clockwise order. On your turn, draw an event card, which forces you to take back one or more of your tokens from the board (healing a city). If it is the last one in this city, the "healing token" on the specific track moves forward and you lose if it meets your marker on that track. The event card also gives you some additional "DNS points", which are akin to money. In the second step of your turn, you spread your virus depending only the methods for infection you have already developed. You gain additional DNS-points for each infection, such as placing new tokens onto the board in the cities. Third, you develop (buy for DNS) more features for your virus like infection via animal, resistance against cold or medicine, or your ability to kill people. Finally, you throw dice according to your skill for killing, and depending on the result, you replace your tokens on the board with dead tokens.
The players win if they have placed all dead tokens in the cities. They lose if the draw pile runs out or the human beings have made enough healing steps on the specific track.
Will you be able to save the planet and reduce the population of the greatest danger for the world — human beings?