title: Seasonal Variation of Common Surgical Site Infections: Does Season Matter?
abstract: OBJECTIVE
  To evaluate seasonal variation in the rate of surgical site infections (SSI) following commonly performed surgical procedures.
  
  
  METHODS
  Retrospective cohort study.
  
  
  METHODS
  We analyzed 6 years (January 1, 2007, through December 31, 2012) of data from the 15 most commonly performed procedures in 20 hospitals in the Duke Infection Control Outreach Network. We defined summer as July through September. First, we performed 3 separate Poisson regression analyses (unadjusted, multivariable, and polynomial) to estimate prevalence rates and prevalence rate ratios of SSI following procedures performed in summer versus nonsummer months. Then, we stratified our results to obtain estimates based on procedure type and organism type. Finally, we performed a sensitivity analysis to test the robustness of our findings.
  
  
  RESULTS
  We identified 4,543 SSI following 441,428 surgical procedures (overall prevalence rate, 1.03/100 procedures). The rate of SSI was significantly higher during the summer compared with the remainder of the year (1.11/100 procedures vs 1.00/100 procedures; prevalence rate ratio, 1.11 [95% CI, 1.04-1.19]; P=.002). Stratum-specific SSI calculations revealed higher SSI rates during the summer for both spinal (P=.03) and nonspinal (P=.004) procedures and revealed higher rates during the summer for SSI due to either gram-positive cocci (P=.006) or gram-negative bacilli (P=.004). Multivariable regression analysis and sensitivity analyses confirmed our findings.
  
  
  CONCLUSIONS
  The rate of SSI following commonly performed surgical procedures was higher during the summer compared with the remainder of the year. Summer SSI rates remained elevated after stratification by organism and spinal versus nonspinal surgery, and rates did not change after controlling for other known SSI risk factors.
authors.affiliation: 1Division of Infectious Diseases,Department of Medicine,Duke University Medical Center,Durham,North Carolina.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Durkin
authors.affiliation: 1Division of Infectious Diseases,Department of Medicine,Duke University Medical Center,Durham,North Carolina.
authors.forename: Kristen V
authors.initials: KV
authors.lastname: Dicks
authors.affiliation: 1Division of Infectious Diseases,Department of Medicine,Duke University Medical Center,Durham,North Carolina.
authors.forename: Arthur W
authors.initials: AW
authors.lastname: Baker
authors.affiliation: 1Division of Infectious Diseases,Department of Medicine,Duke University Medical Center,Durham,North Carolina.
authors.forename: Sarah S
authors.initials: SS
authors.lastname: Lewis
authors.affiliation: 1Division of Infectious Diseases,Department of Medicine,Duke University Medical Center,Durham,North Carolina.
authors.forename: Rebekah W
authors.initials: RW
authors.lastname: Moehring
authors.affiliation: 1Division of Infectious Diseases,Department of Medicine,Duke University Medical Center,Durham,North Carolina.
authors.forename: Luke F
authors.initials: LF
authors.lastname: Chen
authors.affiliation: 1Division of Infectious Diseases,Department of Medicine,Duke University Medical Center,Durham,North Carolina.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Sexton
authors.affiliation: 1Division of Infectious Diseases,Department of Medicine,Duke University Medical Center,Durham,North Carolina.
authors.forename: Deverick J
authors.initials: DJ
authors.lastname: Anderson
mesh_terms: D001407:Bacillus; D016905:Gram-Negative Bacterial Infections / Q000453:epidemiology* / Q000382:microbiology; D016908:Gram-Positive Bacterial Infections / Q000453:epidemiology* / Q000382:microbiology; D006095:Gram-Positive Cocci; D006801:Humans; D015995:Prevalence; D012189:Retrospective Studies; D012621:Seasons; D015144:Southeastern United States / Q000453:epidemiology; D013131:Spine / Q000601:surgery; D013530:Surgical Wound Infection / Q000453:epidemiology*