Berdahl, A.,Brelsford, C.,De Bacco, C.,Dumas, M.,Ferdinand, V.,Grochow, J. A.,H ebert-Dufresne, L.,Kallus, Y.,Kempes, C. P.,Kolchinsky, A.,Larremore, D. B.,Libby, E.,Power, E. A.,Stern, C. A.,Tracey, B. D.
Pathogens can spread epidemically through populations. Beneficial contagions, 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 beneficial biological and social epidemics differ from those of detrimental epidemics? We investigate this question using three theoretical approaches as well as an empirical analysis of concept propagation. First, in evolutionary models, we show that a beneficial horizontally-transmissible element, such as viral DNA, spreads super-exponentially through a population, substantially more quickly than a beneficial mutation. Second, in an epidemiological social network approach we show that infections that cause increased connectivity lead to faster-than-exponential _fixation in the population. Third, in a sociological model with strategic rewiring, we find that preferences for increased global infection accelerate spread and produce super-exponential fixation rates, while preferences for local assortativity halt epidemics by disconnecting the infected from the susceptible. Finally, in an investigation of the Google Ngram corpus, we find that new words and phrases spread super-exponentially, as anticipated by our models. We conclude that the dynamics of beneficial biological and social epidemics are characterized by the remarkably rapid spread of beneficial elements, which can be facilitated in biological systems by horizontal transmission and in social systems by active spreading strategies of infected individuals. Disclaimer: This paper was produced, from conception of idea, to execution, to writing, by a team in just 72 hours (see Appendix A). Although part of our team was working on literature search, we expect that, at this point, our literature review is incomplete. We welcome any additional references for future versions at benepinamics@gmail.com.