Epidemiology of the reported severity of copperhead (Agkistrodon contortrix) snakebite

OBJECTIVE: The goal of this study was to analyze trends in the annual rates of reported medical outcomes of US copperhead (Agkistrodon contortrix) snakebites published in the annual reports of the American Association of Poison Control Centers in the course of 26 years. METHODS: This was a retrospective analysis of medical outcomes for copperhead snakebite victims who developed fatal, major, moderate, minor, or no effects. The annual rates for these medical outcomes were calculated by dividing the annual number of patients in each outcome category by the total annual number of people reported as being bitten by copperheads. Poisson and negative binomial regression were used to examine trends in annual rates. RESULTS: From 1983 through 2008, the incidence rate of copperhead snakebites causing no effect significantly decreased by 12.1%/year (incidence rate ratio [IRR] 0.879; 95% confidence interval [CI] 0.848-0.911]. From 1985 through 2008, the incidence rate of minor outcomes significantly decreased by 2.3%/year (IRR 0.977; 95% CI 0.972-0.981), whereas the rate of moderate outcomes significantly increased by 2.8%/year (IRR 1.028; 95% CI 1.024-1.033). The rate of major outcomes did not significantly change. One fatality was reported in 2001. CONCLUSIONS: Annual rates of copperhead snakebites producing no effects and minor outcomes significantly decreased, those producing moderate outcomes significantly increased, and those producing major outcomes did not significantly change in a 26-year period.