Typically, a system will have three-state cells --- resting, active, and exhausted. A certain number of active cells can activate a resting cell, which thereupon enters into the exhausted state for several generations. Once the recovery time has elapsed, a cell rests until activated anew.
Activity has many interpretations: initiation of a chemical reaction, infection with a disease, enthusiasm over hearing a rumor. Exhaustion runs a similar gamut: overheating or depletion of the reactants, incubation of the disease, boredom.