Dynamics of beneficial epidemics

Pathogens can spread epidemically through populations. Beneficialcontagions, such as viruses that enhance host survival or technological innovations that improve quality of life, also have the potential to spread epidemically. How do the dynamics of beneficialbiological and social epidemics differ from those of detrimental epidemics? We investigate this question using a breadth-first modeling approach involving three distinct theoretical models. First, in the context of population genetics, we show that a horizontally-transmissibleelement that increases fitness, such as viral DNA, spreads superexponentially through a population, more quickly than a beneficialmutation. Second, in the context of behavioral epidemiology, we show that infections that cause increased connectivity lead to superexponential fixation in the population. Third, in the context of dynamic social networks, we find that preferences for increased global infection accelerate spread and produce superexponential fixation, but preferences for local assortativity halt epidemics by disconnecting the infected from the susceptible. We conclude that the dynamics of beneficialbiological and social epidemics are characterized by the rapid spread of beneficialelements, which is facilitated in biological systems by horizontal transmissionand in social systems by active spreading behavior of infected individuals.