Spatial and temporal clustering of patients hospitalized with laboratory-confirmed influenza in the United States
Chantel Sloan,
Rameela Chandrasekhar,
Edward Mitchel,
Danielle Ndi,
Lisa Miller,
Ann Thomas,
Nancy M. Bennett,
Shua Chai,
Melanie Spencer,
Seth Eckel,
Nancy Spina,
Maya Monroe,
Evan J. Anderson,
Ruth Lynfield,
Kimberly Yousey-Hindes,
Marisa Bargsten,
Shelley Zansky,
Krista Lung,
Monica Schroeder,
Charisse N Cummings,
Shikha Garg,
William Schaffner,
Mary Lou Lindegren
Affiliations
Chantel Sloan
Brigham Young University, Provo, UT, USA; Corresponding author at: Department of Public Health, Brigham Young University, Life Sciences Building, 2048, Provo, UT, 84601, USA.
Rameela Chandrasekhar
New Mexico Department of Health, NM, USA
Edward Mitchel
Vanderbilt University School of Medicine, Nashville, TN, USA
Danielle Ndi
Vanderbilt University School of Medicine, Nashville, TN, USA
Lisa Miller
University of Colorado, School of Public Health, Aurora, CO, USA
Ann Thomas
Oregon Department of Public Health, OR, USA
Nancy M. Bennett
University of Rochester School of Medicine and Dentistry, NY, USA
Shua Chai
California Emerging Infections Program, Oakland, CA, USA
Melanie Spencer
Salt Lake County Health Department, CO, USA
Seth Eckel
Michigan Department of Health and Human Services, MI, USA
Nancy Spina
New York State Department of Health, NY, USA
Maya Monroe
Maryland Department of Health, MD, USA
Evan J. Anderson
Emory University School of Medicine and the Georgia Emerging Infections Program, Atlanta VAMC, Atlanta, GA, USA
Ruth Lynfield
Minnesota Department of Health, MN, USA
Kimberly Yousey-Hindes
Connecticut Emerging Infections Program, Yale School of Public Health, New Haven, CT, USA
Marisa Bargsten
New Mexico Department of Health, NM, USA
Shelley Zansky
New York State Department of Health, NY, USA
Krista Lung
Ohio Department of Health, Columbus, OH, USA
Monica Schroeder
Council of State and Territorial Epidemiologists, Atlanta, GA, USA
Charisse N Cummings
Influenza Division, CDC, Atlanta, GA, USA
Shikha Garg
Influenza Division, CDC, Atlanta, GA, USA
William Schaffner
Vanderbilt University School of Medicine, Nashville, TN, USA
Mary Lou Lindegren
Vanderbilt University School of Medicine, Nashville, TN, USA
Background: Timing of influenza spread across the United States is dependent on factors including local and national travel patterns and climate. Local epidemic intensity may be influenced by social, economic and demographic patterns. Data are needed to better explain how local socioeconomic factors influence both the timing and intensity of influenza seasons to result in national patterns. Methods: To determine the spatial and temporal impacts of socioeconomics on influenza hospitalization burden and timing, we used population-based laboratory-confirmed influenza hospitalization surveillance data from the CDC-sponsored Influenza Hospitalization Surveillance Network (FluSurv-NET) at up to 14 sites from the 2009/2010 through 2013/2014 seasons (n = 35,493 hospitalizations). We used a spatial scan statistic and spatiotemporal wavelet analysis, to compare temporal patterns of influenza spread between counties and across the country. Results: There were 56 spatial clusters identified in the unadjusted scan statistic analysis using data from the 2010/2011 through the 2013/2014 seasons, with relative risks (RRs) ranging from 0.09 to 4.20. After adjustment for socioeconomic factors, there were five clusters identified with RRs ranging from 0.21 to 1.20. In the wavelet analysis, most sites were in phase synchrony with one another for most years, except for the H1N1 pandemic year (2009–2010), wherein most sites had differential epidemic timing from the referent site in Georgia. Conclusions: Socioeconomic factors strongly impact local influenza hospitalization burden. Influenza phase synchrony varies by year and by socioeconomics, but is less influenced by socioeconomics than is disease burden.
