About the Authors

Alison L. Hill

alhill@fas.harvard.edu

Affiliations Program for Evolutionary Dynamics, Harvard University, Cambridge, Massachusetts, United States of America, Biophysics Program and Harvard-MIT Division of Health Sciences and Technology, Harvard University, Cambridge, Massachusetts, United States of America

David G. Rand

Affiliations Program for Evolutionary Dynamics, Harvard University, Cambridge, Massachusetts, United States of America, Department of Psychology and Berkman Center for Internet and Society, Harvard University, Cambridge, Massachusetts, United States of America

Martin A. Nowak

Affiliations Program for Evolutionary Dynamics, Harvard University, Cambridge, Massachusetts, United States of America, Department of Mathematics, Harvard University, Cambridge, Massachusetts, United States of America, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America

Nicholas A. Christakis

Affiliations Department of Medicine, Harvard Medical School, Boston, Massachusetts, United States of America, Department of Health Care Policy, Harvard Medical School, Boston, Massachusetts, United States of America, Department of Sociology, Harvard University, Cambridge, Massachusetts, United States of America

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

Analyzed the data: ALH. Wrote the paper: ALH DGR. Conceived and designed the mathematical model and analysis: ALH DGR MAN NAC.