About the Authors

Vittoria Colizza

Affiliations School of Informatics and Center for Biocomplexity, Indiana University, Bloomington, Indiana, United States of America , Complex Networks Lagrange Laboratory, Institute for Scientific Interchange Foundation, Turin, Italy

Alain Barrat

Affiliations Complex Networks Lagrange Laboratory, Institute for Scientific Interchange Foundation, Turin, Italy , Unité Mixte de Recherche 8627, Centre National de la Recherche Scientifique, Université Paris-Sud, Orsay, France

Marc Barthelemy

Affiliations School of Informatics and Center for Biocomplexity, Indiana University, Bloomington, Indiana, United States of America , Commissariat à l'Energie Atomique, Direction Ile-de-France, Centre d'Etudes de Bruyères Le Châtel, Bruyères Le Châtel, France

Alain-Jacques Valleron

Affiliations Unité de Recherche en Epidémiologie, Systèmes d'Information et Modélisation, Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche 707, Université Pierre et Marie Curie, Paris, France , Hôpital Saint-Antoine, Assistance Publique-Hôpitaux de Paris, Paris, France

Alessandro Vespignani

To whom correspondence should be addressed. E-mail: alexv@indiana.edu

Affiliations School of Informatics and Center for Biocomplexity, Indiana University, Bloomington, Indiana, United States of America , Complex Networks Lagrange Laboratory, Institute for Scientific Interchange Foundation, Turin, Italy

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

VC, AB, MB, AJV, and AV designed the study and analyzed the data. VC, AB, MB, AJV, and AV contributed to writing the paper. VC, AB, MB, and AV collected data or did experiments for the study.