Background

In the Americas, yellow fever virus transmission is a latent threat due to the proximity between urban and wild environments. Although yellow fever has nearly vanished from North and Central America, there are still 13 countries in the Americas considered endemic by the World Health Organization. Human cases usually occur as a result of the exposure to sylvatic yellow fever in tropical forested environments; but urban outbreaks reported during the last decade demonstrate that the risk in this environment still exists. The objective of this study was to identify spatial patterns and the relationship between key geographic and environmental factors with the distribution of yellow fever human cases in the Americas.

Methodology/Principal findings

An ecological study was carried out to analyze yellow fever human cases reported to the Pan American Health Organization from 2000 to 2014, aggregated by second administrative level subdivisions (counties). Presence of yellow fever by county was used as the outcome variable and eight geo-environmental factors were used as independent variables. Spatial analysis was performed to identify and examine natural settings per county. Subsequently, a multivariable logistic regression model was built. During the study period, 1,164 cases were reported in eight out of the 13 endemic countries. Nearly 83.8% of these cases were concentrated in three countries: Peru (37.4%), Brazil (28.1%) and Colombia (18.4%); and distributed in 57 states/provinces, specifically in 286 counties (3.4% of total counties). Yellow fever presence was significantly associated with altitude, rain, diversity of non-human primate hosts and temperature. A positive spatial autocorrelation revealed a clustered geographic pattern in 138/286 yellow fever positive counties (48.3%).

Conclusions/Significance

A clustered geographic pattern of yellow fever was identified mostly along the Andes eastern foothills. This risk map could support health policies in endemic countries. Geo-environmental factors associated with presence of yellow fever could help predict and adjust the limits of other risk areas of epidemiological concern.

中文翻译：

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美洲与人类黄热病相关的地理格局和环境因素

背景

在美洲，由于城市环境和野生环境之间的邻近性，黄热病病毒的传播是一种潜在的威胁。尽管北美和中美洲的黄热病几乎消失了，但美洲仍有13个国家被世界卫生组织认为是地方病。人间病例通常是由于在热带森林环境中暴露于丁香黄热而引起的。但过去十年间报道的城市暴发表明，这种环境下的风险仍然存在。这项研究的目的是确定美洲黄热病人类病例分布的空间格局以及关键地理和环境因素之间的关系。

方法/主要发现

进行了一项生态研究，以分析2000年至2014年间报告给泛美卫生组织的黄热病人类病例，并按第二行政级别分区（县）进行汇总。县使用黄热病作为结果变量，八个地理环境因素用作自变量。进行了空间分析，以识别和检查每个县的自然环境。随后，建立了多元逻辑回归模型。在研究期间，在13个流行国家中有8个报告了1,164例病例。其中近83.8％的案件集中在三个国家：秘鲁（37.4％），巴西（28.1％）和哥伦比亚（18.4％）；分布在57个州/省，特别是286个县（占县总数的3.4％）。黄热病的存在与海拔，雨水，非人类灵长类动物宿主的多样性和温度显着相关。积极的空间自相关揭示了138/286个黄热病阳性县（48.3％）的集群地理格局。

结论/意义

黄热的集群地理格局主要在安第斯山脉东麓丘陵地区发现。该风险图可以支持流行国家的卫生政策。与黄热病相关的地质环境因素可以帮助预测和调整流行病学关注的其他危险区域的范围。