contagion

(kən-tāˈjən)

1. a. Disease transmission by direct or indirect contact.
   b. A disease that is or may be transmitted by direct or indirect contact; a contagious disease.
   c. The direct cause, such as a bacterium or virus, of a communicable disease.
2. Psychology The spread of a behavior pattern, attitude, or emotion from person to person or group to group through suggestion, propaganda, rumor, or imitation.
3. A harmful, corrupting influence: feared that violence on television was a contagion affecting young viewers.
4. The tendency to spread, as of a doctrine, influence, or emotional state.