Impact of environmental factors on neglected emerging arboviral diseases

BackgroundBrazil is a tropical country that is largely covered by rainforests and other natural ecosystems, which provide ideal conditions for the existence of many arboviruses. However, few analyses have examined the associations between environmental factors and arboviral diseases. Thus, based on the hypothesis of correlation between environment and epidemiology, the proposals of this study were (1) to obtain the probability of occurrence of Oropouche, Mayaro, Saint Louis and Rocio fevers in Brazil based on environmental conditions corresponding to the periods of occurrence of the outbreaks; (2) to describe the macroclimatic scenario in Brazil in the last 50 years, evaluating if there was any detectable tendency to increase temperatures and (3) to model future expansion of those arboviruses in Brazil based on future temperature projections.Methodology/Principal findingsOur model assessed seven environmental factors (annual rainfall, annual temperature, elevation, seasonality of temperature, seasonality of precipitation, thermal amplitude, and daytime temperature variation) for their association with the occurrence of outbreaks in the last 50 years. Our results suggest that various environmental factors distinctly influence the distribution of each arbovirus, with temperature being the central determinant of disease distribution in all high-risk areas. These areas are subject to change, since the average temperature of some areas has increased significantly over the time.Conclusions/SignificanceThis is the first spatio-temporal study of the Oropouche, Mayaro, Saint Louis, and Rocio arboviruses, and our results indicate that they may become increasingly important public health problems in Brazil. Thus, next studies and control programs should include these diseases and also take into consideration key environmental elements.研究背景 巴西作为热带国家，境内广泛覆盖热带雨林与其他自然生态系统，为多种虫媒病毒（arboviruses）的生存繁衍提供了理想条件。然而目前鲜有研究探讨环境因素与虫媒病毒病之间的关联。本研究基于环境与流行病学存在相关性这一假说，设定了三项研究目标：其一，依据暴发流行时期对应的环境条件，推演巴西境内奥罗普切热（Oropouche fever）、马亚罗热（Mayaro fever）、圣路易斯热（Saint Louis fever）及罗西奥热（Rocio fever）的发生概率；其二，梳理巴西近50年的宏观气候格局，评估是否存在可检测到的气温升高趋势；其三，基于未来气温预测数据，构建上述虫媒病毒在巴西境内的未来扩散模型。 研究方法与主要发现 本研究模型评估了7项环境因素与近50年病毒暴发事件的关联，分别为年降雨量、年平均气温、海拔高度、气温季节变率、降水季节变率、气温日较差与日间气温波动。结果显示，不同环境因素对每种虫媒病毒的分布存在差异化影响，而气温是所有高风险区域疾病分布的核心决定因素。由于部分区域的平均气温已出现显著升高，这些高风险区域的范围或将发生变化。 结论与意义 本研究是首项针对奥罗普切热、马亚罗热、圣路易斯热及罗西奥热相关虫媒病毒的时空分布研究，结果表明上述疾病或将成为巴西日益严峻的公共卫生问题。因此，后续研究与防控项目应将此类疾病纳入考量范围，并重点关注关键环境要素。