About the Authors

Martha I Nelson

Affiliation Center for Infectious Disease Dynamics, Department of Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America

Lone Simonsen

Affiliation National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America

Cecile Viboud

Affiliation Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America

Mark A Miller

Affiliation Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America

Jill Taylor

Affiliation Wadsworth Center, New York State Department of Health, Albany, New York, United States of America

Kirsten St George

Affiliation Wadsworth Center, New York State Department of Health, Albany, New York, United States of America

Sara B Griesemer

Affiliation Wadsworth Center, New York State Department of Health, Albany, New York, United States of America

Elodie Ghedin

Affiliation The Institute for Genomic Research, Rockville, Maryland, United States of America

Naomi A Sengamalay

Affiliation The Institute for Genomic Research, Rockville, Maryland, United States of America

David J Spiro

Affiliation The Institute for Genomic Research, Rockville, Maryland, United States of America

Igor Volkov

Affiliation Center for Infectious Disease Dynamics, Department of Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America

Bryan T Grenfell

Affiliations Center for Infectious Disease Dynamics, Department of Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America , Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America

David J Lipman

Affiliation National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, United States of America

Jeffery K Taubenberger

Affiliation Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America

Edward C Holmes

To whom correspondence should be addressed. E-mail: ech15@psu.edu

Affiliations Center for Infectious Disease Dynamics, Department of Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America , Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

MIN and ECH conceived the study and wrote the paper, with contributions from all other authors. JT, KSG, and SGB collected the viral samples. EG, NAS, and DJS undertook the viral genome sequencing. LS, CV, MAM, and BTG advised on epidemiological aspects of the study. MIN, IV, and ECH performed the sequence analysis. DJL and JKT wrote the paper.