Effects of seasonal changes in temperature and humidity on incidence of necrotizing soft tissue infections in Halifax, Canada, 2001-2015

OBJECTIVES: To explore weather seasonal variation in Necrotizing soft tissue infections (NSTI) in Halifax, Nova Scotia, Canada could be attributed to changes in environmental factors of temperature and humidity specifically. METHODS: A retrospective chart review of NSTIs between 2001 and 2015. Regional temperature and humidity data were obtained from the Environment Canada Agency, Halifax, Canada. Chi-square was used for categorical variables and continuous data was used for correlation analyses. Logistic regression was performed to analyze mortality. RESULTS: Of 170 NSTI patients identified, more presented from March to July, especially when the temperature was >10ºC. Higher incidence per 100,000 persons correlated with increased monthly temperatures (p<0.01). Monthly NSTI incidence was inversely related to mean humidity (p=0.005). Causative organism was associated with mean weekly temperature (p<0.01) but not humidity (p=0.66). Low body mass index, higher American Society of Anesthesiologists class, long intensive care unit stay, and shorter overall hospital stay were associated with mortality. No correlation was identified between temperature and humidity and mortality. CONCLUSION: This study demonstrates a tendency toward more frequent cases of NSTI with warmer, but less humid weather, without effect on severity or mortality.