Typhoid fever in Santiago, Chile: Insights from a mathematical model utilizing venerable archived data from a successful disease control program
Typhoid fever in Santiago, Chile: Insights from a mathematical model utilizing venerable archived data from a successful disease control program
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DOI：
10.1371/journal.pntd.0006759
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发表时间：
2018-09-01
影响因子：
3.8
通讯作者：
Levine, Myron M.
中科院分区：
文献类型：
--
作者：
Gauld, Jillian S.;Hu, Hao;Levine, Myron M.
伤寒是许多发展中国家的地方病。在世纪早期，包括美国在内的新兴工业化国家成功地控制了伤寒，因为水处理（氯化/砂滤）和改善的卫生条件变得普遍。令人费解的是，尽管智利的圣地亚哥有饮用水和广泛的家庭卫生设施，但伤寒在20世纪80年代仍然是地方病。在圣地亚哥的地方性和控制的多个阶段收集数据，为深入了解现代环境中的传播驱动因素提供了独特的资源。我们开发了一个基于个体的伤寒传播数学模型，模型的组成部分包括长周期和短周期传播途径之间的区别。用于拟合模型的数据包括慢性携带者的患病率、季节性、纵向发病率和伤寒感染和疾病的年龄特异性分布。我们的模型捕捉到了圣地亚哥在地方病、疫苗接种和环境控制方面的动态。接种疫苗和减少暴露于季节性放大的长周期传播都有助于观察到的伤寒发病率下降，估计疫苗会引起群体效应。疫苗是控制地方性伤寒的重要工具，在这种情况下，即使是有限的覆盖率也会引起群体效应。消除负责扩大长周期传播的车辆和评估慢性携带者在地方性环境中的作用是设计加速控制地方性伤寒的方案的其他关键因素。
Typhoid fever is endemic in many developing countries. In the early 20th century, newly industrializing countries including the United States successfully controlled typhoid as water treatment (chlorination/sand filtration) and improved sanitation became widespread. Enigmatically, typhoid remained endemic through the 1980s in Santiago, Chile, despite potable municipal water and widespread household sanitation. Data were collected across multiple stages of endemicity and control in Santiago, offering a unique resource for gaining insight into drivers of transmission in modern settings. We developed an individual-based mathematical model of typhoid transmission, with model components including distinctions between long-cycle and short-cycle transmission routes. Data used to fit the model included the prevalence of chronic carriers, seasonality, longitudinal incidence, and age-specific distributions of typhoid infection and disease. Our model captured the dynamics seen in Santiago across endemicity, vaccination, and environmental control. Both vaccination and diminished exposure to seasonal amplified long-cycle transmission contributed to the observed declines in typhoid incidence, with the vaccine estimated to elicit herd effects. Vaccines are important tools for controlling endemic typhoid, with even limited coverage eliciting herd effects in this setting. Removing the vehicles responsible for amplified long-cycle transmission and assessing the role of chronic carriers in endemic settings are additional key elements in designing programs to achieve accelerated control of endemic typhoid.