Ackley Sarah F, Liu Fengchen, Porco Travis C, Pepperell Caitlin S
Department of Epidemiology and Biostatistics, University of California San Francisco , San Francisco, CA , USA ; Proctor Foundation, University of California San Francisco , San Francisco, CA , USA.
Department of Epidemiology and Biostatistics, University of California San Francisco , San Francisco, CA , USA.
PeerJ. 2015 Sep 24;3:e1237. doi: 10.7717/peerj.1237. eCollection 2015.
Late 19th century epidemics of tuberculosis (TB) in Western Canadian First Nations resulted in peak TB mortality rates more than six times the highest rates recorded in Europe. Using a mathematical modeling approach and historical TB mortality time series, we investigate potential causes of high TB mortality and rapid epidemic decline in First Nations from 1885 to 1940. We explore two potential causes of dramatic epidemic dynamics observed in this setting: first, we explore effects of famine prior to 1900 on both TB and population dynamics. Malnutrition is recognized as an individual-level risk factor for TB progression and mortality; its population-level effects on TB epidemics have not been explored previously. Second, we explore effects of heterogeneity in susceptibility to TB in two ways: modeling heterogeneity in susceptibility to infection, and heterogeneity in risk of developing disease once infected. Our results indicate that models lacking famine-related changes in TB parameters or heterogeneity result in an implausibly poor fit to both the TB mortality time series and census data; the inclusion of these features allows for the characteristic decline and rise in population observed in First Nations during this time period and confers improved fits to TB mortality data.
19世纪末，加拿大西部原住民中爆发的结核病（TB）疫情导致结核病死亡率峰值超过欧洲最高纪录的六倍多。我们采用数学建模方法并结合历史结核病死亡率时间序列，研究了1885年至1940年期间原住民结核病高死亡率和疫情迅速下降的潜在原因。我们探讨了在这种情况下观察到的疫情动态剧烈变化的两个潜在原因：第一，我们探讨了1900年之前饥荒对结核病和人口动态的影响。营养不良被认为是结核病进展和死亡的个体层面风险因素；其在人群层面上对结核病疫情的影响此前尚未得到研究。第二，我们从两个方面探讨了结核病易感性异质性的影响：对感染易感性的异质性进行建模，以及对感染后发病风险的异质性进行建模。我们的结果表明，缺乏与饥荒相关的结核病参数变化或异质性的模型，对结核病死亡率时间序列和人口普查数据的拟合效果差得难以置信；纳入这些特征能够解释这一时期原住民人口中观察到的特征性下降和增长情况，并使模型对结核病死亡率数据的拟合度得到改善。
