Program Schedule

Seasonal Variation of Surgical Site Infections Following Common Procedures

Session: Poster Abstract Session: HAI Surveillance and Public Reporting
Friday, October 10, 2014
Room: The Pennsylvania Convention Center: IDExpo Hall BC
Background: The relationship between time of year and surgical site infection (SSI) has not been well studied. We examined seasonal variation of SSI in a large cohort of patients in non-teaching community hospitals.

Methods: We performed a cohort study of patients undergoing the 10 procedures in 20 community hospitals affiliated with the Duke Infection Control Outreach Network from 1/1/2007-12/31/2012. SSIs were defined using National Healthcare Safety Network criteria and identified using standardized surveillance methods. Summer was defined as July through September. The prevalence rate (PR) of SSI during the summer was compared to the remainder of the year by calculating PR ratios (PRR) and 95% confidence intervals. Procedure and organism type were examined by stratified analysis.  

Results: We identified 3,182 SSIs following 361,857 surgical procedures (overall PR=0.88/100 procedures). The most common pathogens were S. aureus (1450; 46%), coagulase negative Staphylococci (342; 11%), and E.coli(213; 6.7%). The overall rate of SSI during the summer months was significantly higher than the rate during the remainder of the year (0.97/100 vs. 0.85/100 procedures; PRR 1.16, p<0.001).  The rates of SSIs were higher in summer months for infections caused by Gram positive cocci (PRR: 1.15, p=0.005) and Gram negative bacilli (PRR: 1.29, p=0.001). Seven out of the ten procedures demonstrated higher SSI rates during the summer (table).  

Conclusion:  To our knowledge, this is the first study to demonstrate seasonal variation of SSI in non-spinal surgery procedures.  Higher SSI rates were observed during the summer regardless of organism and in several different procedure types.  Further studies are needed to understand reasons for these findings.

Table. SSI rate by season using Chi square analysis with stratification by organism group.


SSI Cases for “Summer”

Prevalence Rate for Summer /100 surgeries

SSI Cases for “Rest of Year”

Prevalence Rate for “Rest of Year” /100 surgeries

Prevalence Rate Ratio

P value



0.97 (0.91,1.03)


0.85 (0.81,0.88)

1.16 (1.06,1.26)


Gram positive cocci


0.64 (0.59,0.69)


0.56 (0.53,0.59)

1.15 (1.04,1.26)


Gram negative rods


0.24 (0.21,0.28)


0.19 (0.17,0.21)

1.29 (1.10,1.51)




0.18 (0.15,0.20)


0.18 (0.16,0.19)

1.00 (0.84,1.20)


Michael J. Durkin, MD1, Kristen V. Dicks, MD1, Arthur W. Baker, MD2, Rebekah W. Moehring, MD, MPH1, Sarah S. Lewis, MD1, Luke F. Chen, MBBS, MPH, CIC, FRACP1, Daniel J. Sexton, MD, FIDSA1 and Deverick Anderson, MD, MPH2, (1)Division of Infectious Diseases, Duke University Medical Center, Durham, NC, (2)Duke University Medical Center, Durham, NC


M. J. Durkin, None

K. V. Dicks, None

A. W. Baker, None

R. W. Moehring, None

S. S. Lewis, None

L. F. Chen, None

D. J. Sexton, UpToDate: Editor, Royalties
National Football League: Consultant, Consulting fee and Educational grant
Cubist: Grant Investigator, Grant recipient
Johnson and Johnson: Consultant, Consulting fee

D. Anderson, None

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