Termination of the ice bucket challenge

ABSTRACT The ice bucket challenge is a social game aimed at encouraging donations to the amyotrophic lateral sclerosis association. The rules imply that each participant challenges each recruited follower to dump a bucket of ice water on his or her head. The network of who has nominated whom has a tree structure. The short duration of the ice bucket challenge is explained by using the reproduction number , under the assumption that the capacity to recruit followers varies with the participant. The epidemic lasts until the interruption of the transmission tree occurring well before the depletion of susceptible followers. Such a tree is reconstructed from publicly available contact data and the interest in this game.