Epidemiology of severe and fatal rattlesnake bites published in the American Association of Poison Control Centers' Annual Reports.

Introduction: No study has focused on the nationwide epidemiology of severe and fatal rattlesnake bites during the last 25 years. We examined rates and temporal trends of severe and fatal rattlesnake bites across the United States. Our hypothesis was that nationwide annual rates of both severe and fatal outcomes from rattlesnake bites have remained unchanged over time.

Methods: This study retrospectively analyzed all human rattlesnake bites published in the Annual Reports of the American Association of Poison Control Centers from 1983 through 2007. Annual rates of severe (major) and fatal rattlesnake bites were calculated using the annual number of major outcomes and fatalities as respective numerators and the total annual number of single rattlesnake bites (exposures) as denominators. Negative binomial and Poisson regressions were used to examine trends of severe and fatal rattlesnake bites over time.

Results: Annually, from 1985 to 2007, the incidence rate of major outcomes decreased by 2% per year (incidence rate ratio = 0.980; CI = 0.967-0.993), corresponding to an absolute annual rate decrease of two major outcomes per 1,000 bites per year. Annual rates of fatalities showed no statistically significant change from 1983 through 2007.

Conclusion: This is the first study to examine rates and trends of published severe and fatal rattlesnake bites across the United States over the past 25 years. Annual rates of severe rattlesnake bites, derived from the published Annual Reports of the American Association of Poison Control Centers, have significantly decreased over time, whereas rates of fatal rattlesnake bites have remained unchanged.