title: Local spatial and temporal processes of influenza in Pennsylvania, USA: 2003-2009.
abstract: BACKGROUND
  Influenza is a contagious respiratory disease responsible for annual seasonal epidemics in temperate climates. An understanding of how influenza spreads geographically and temporally within regions could result in improved public health prevention programs. The purpose of this study was to summarize the spatial and temporal spread of influenza using data obtained from the Pennsylvania Department of Health's influenza surveillance system.
  
  
  RESULTS
  We evaluated the spatial and temporal patterns of laboratory-confirmed influenza cases in Pennsylvania, United States from six influenza seasons (2003-2009). Using a test of spatial autocorrelation, local clusters of elevated risk were identified in the South Central region of the state. Multivariable logistic regression indicated that lower monthly precipitation levels during the influenza season (OR = 0.52, 95% CI: 0.28, 0.94), fewer residents over age 64 (OR = 0.27, 95% CI: 0.10, 0.73) and fewer residents with more than a high school education (OR = 0.76, 95% CI: 0.61, 0.95) were significantly associated with membership in this cluster. In addition, time series analysis revealed a temporal lag in the peak timing of the influenza B epidemic compared to the influenza A epidemic.
  
  
  CONCLUSIONS
  These findings illustrate a distinct spatial cluster of cases in the South Central region of Pennsylvania. Further examination of the regional transmission dynamics within these clusters may be useful in planning public health influenza prevention programs.
authors.affiliation: New York City Department of Health and Mental Hygiene, New York, New York, United States of America. jstark@health.nyc.gov
authors.forename: James H
authors.initials: JH
authors.lastname: Stark
authors.forename: Ravi
authors.initials: R
authors.lastname: Sharma
authors.forename: Stephen
authors.initials: S
authors.lastname: Ostroff
authors.forename: Derek A T
authors.initials: DA
authors.lastname: Cummings
authors.forename: Bard
authors.initials: B
authors.lastname: Ermentrout
authors.forename: Samuel
authors.initials: S
authors.lastname: Stebbins
authors.forename: Donald S
authors.initials: DS
authors.lastname: Burke
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Wisniewski
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D016000:Cluster Analysis; D005260:Female; D006801:Humans; D007223:Infant; D007251:Influenza, Human / Q000453:epidemiology* / Q000635:transmission; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D010414:Pennsylvania / Q000453:epidemiology; D011891:Rain; D012621:Seasons; D012959:Socioeconomic Factors; D013997:Time Factors; D055815:Young Adult