Snakebites and climate change in California, 1997–2017

<b>Background:</b> Climate change effect on flora and fauna has been scientifically documented, but the effect on North American venomous snakebites is unknown. The objectives were to examine Californian snakebite incidence and correlate with weather patterns and climate changes. <b>Methods:</b> A retrospective analysis of snakebites reported to the Californian Poison Control System from 1 September 1997 to 30 September 2017. Venomous snakebite reports were aggregated by caller zip code, and correlated per county with weather data, air temperature, precipitation, population data, eco-regions, and land characteristics. Time series decomposition by seasonality and trend, regression, and autocorrelation were used to assess association between climate variables and incidence. <b>Results:</b> There were 5365 reported venomous snakebites during the study period, with a median age of 37 years (22–51) with 76% male (<i>p</i> p = .65). The snakebite incidence per million people rose after a period of no drought and declined during drought (<i>r</i> = −0.41, <i>p</i> ≪ .01). Snakebite incidence decreased by 6-month prior drought (−3.8% for each 10% increase in drought), and increased by 18-month prior precipitation (+3.9% for each 10% increase in precipitation). <b>Conclusions:</b> Patterns of precipitation and drought had a significant and predictive effect on snakebites in California over a 20-year period. Snakebite incidence decreased following drought, and increased after precipitation.

**背景**：气候变化对动植物群（flora and fauna）的影响已被科学文献证实，但其对北美有毒蛇咬伤（venomous snakebites）事件的影响尚不明确。本研究旨在调查加利福尼亚州的蛇咬伤发病率，并分析其与天气模式及气候变化的相关性。
**方法**：本研究对1997年9月1日至2017年9月30日期间上报至加利福尼亚毒物管控系统（Californian Poison Control System）的蛇咬伤病例进行回顾性分析。以上报者的邮政编码为单位对有毒蛇咬伤报告进行汇总，并按县别将数据与气象数据、气温、降水量、人口数据、生态区域及土地特征进行关联分析。采用基于季节与趋势的时间序列分解、回归分析及自相关分析，评估气候变量与蛇咬伤发病率之间的相关性。
**结果**：研究期间共上报有毒蛇咬伤病例5365例，患者中位年龄为37岁（四分位间距22~51岁），男性占比76%（P=0.65）。无干旱时段后，加利福尼亚州每百万人蛇咬伤发病率有所上升，而干旱时段发病率则下降（相关系数r=-0.41，P≪0.01）。蛇咬伤发病率与此前6个月的干旱程度呈负相关（干旱程度每升高10%，发病率降低3.8%），与此前18个月的降水量呈正相关（降水量每升高10%，发病率升高3.9%）。
**结论**：在20年的研究周期内，降水量与干旱模式对加利福尼亚州蛇咬伤事件存在显著且可预测的影响。蛇咬伤发病率在干旱时段后降低，而在降水时段后升高。