Lower extremity cellulitis (LEC) is common in clinical practice; this prompted our interest in evaluating microbiologic and epidemiologic aspects of this syndrome. The population-based unadjusted incidence of LEC in Olmsted County (OC), MN was reported to be 199 per 100,000 persons prior to the emergence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) in 1999. Since its emergence, it is not known whether CA-MRSA has affected the incidence of LEC, but some empiric treatment recommendations include coverage for this organism. Effects of seasonality on incidence of infectious diseases have been described for other entities, but scant published data report the effect of seasonality on the incidence of LEC. We sought to determine the incidence of and effect of seasonality on LEC in a contemporary population since the emergence of CA-MRSA.
This retrospective, population-based study was conducted among adults with LEC living in OC in 2013. Patients were selected for chart review based on the presence of ICD-9 codes for LEC. Included patients were adults with a first episode of LEC for the year 2013. Patients with purulent skin/soft tissue infections were excluded. Poisson regression was used to assess the influence of age, sex and seasonal effects on incidence.
Based on 195 patients fulfilling inclusion criteria, the adjusted incidence (per 100,000 persons) of LEC in our population-based cohort was 176.6 (151.5, 201.7). Sex specific incidence (per 100,000) differed significantly, with rates of 133.3 (104.1, 162.5) and 225.8 (183.5, 268.0) in females and males, respectively. A seasonal effect was seen in incidence of LEC, with rates (per 100,000) of 224.6 (180.9, 268.4) in warmer months (May-September) compared to 142.3 (112.8, 171.9) in colder months (October-April).
Despite the emergence of CA-MRSA in 1999 and its rising prevalence, the incidence of LEC was lower in 2013 compared to that in 1999, particularly among females. This suggests that CA-MRSA is not significant as a cause of LEC and empiric coverage of CA-MRSA may not be needed. Cases of LEC are seasonally distributed, with more cases occurring in spring/summer months. A reanalysis of risk factor modification is needed.
J. R. Marcelin,
E. M. Tan, None
B. Lahr, None
L. M. Baddour, None