Institute for Veterinary Public Health, University of Veterinary Medicine Vienna, Veterinärplatz 1, A-1210 Vienna, Austria.
Prev Vet Med. 2011 Feb 1;98(2-3):99-110. doi: 10.1016/j.prevetmed.2010.10.013. Epub 2010 Nov 20.
The West Nile virus (WNV) is an arthropod-borne virus (arbovirus) circulating in a natural transmission cycle between mosquitoes (enzootic vectors) and birds (amplifying hosts). Additionally, mainly horses and humans (dead-end hosts) may be infected by blood-feeding mosquitoes (bridge vectors). We developed an epidemic model for the simulation of the WNV dynamics of birds, horses and humans in the U.S., which we apply to the Minneapolis metropolitan area (Minnesota). The SEIR-type model comprises a total of 19 compartments, that are 4 compartments for mosquitoes and 5 compartments or health states for each of the 3 host species. It is the first WNV model that simulates the seasonal cycle by explicitly considering the environmental temperature. The latter determines model parameters responsible for the population dynamics of the mosquitoes and the extrinsic incubation period. Once initialized, our WNV model runs for the entire period 2002-2009, exclusively forced by environmental temperature. Simulated incidences are mainly determined by host and vector population dynamics, virus transmission and herd immunity, respectively. We adjusted our WNV model to fit monthly totals of reported bird, equine and human cases in the Minneapolis metropolitan area. From this process we estimated that the proportion of actually WNV-induced dead birds reported by the Centers for Disease Control and Prevention is about 0.8%, whereas 7.3% of equine and 10.7% of human cases were reported. This is consistent with referenced expert opinions whereby about 10% of equine and human cases are symptomatic (the other 90% of asymptomatic cases are usually not reported). Despite the restricted completeness of surveillance data and field observations, all major peaks in the observed time series were caught by the simulations. Correlation coefficients between observed and simulated time series were R=0.75 for dead birds, R=0.96 for symptomatic equine cases and R=0.86 for human neuroinvasive cases, respectively.
西尼罗河病毒（WNV）是一种虫媒病毒（arbovirus），在蚊子（内媒传播媒介）和鸟类（扩增宿主）之间的自然传播循环中循环。此外，主要是马和人类（终末宿主）可能会被吸血蚊子（桥梁传播媒介）感染。我们开发了一种用于模拟美国鸟类、马和人类WNV 动态的流行模型，我们将其应用于明尼阿波利斯大都市区（明尼苏达州）。SEIR 型模型共包含 19 个隔室，其中 4 个隔室用于蚊子，3 个宿主物种中的每一个都有 5 个隔室或健康状态。这是第一个通过明确考虑环境温度来模拟季节性循环的 WNV 模型。后者确定了负责蚊子种群动态和外潜伏期的模型参数。一旦初始化，我们的 WNV 模型仅在环境温度的驱动下运行整个 2002-2009 年期间。模拟的发病率主要取决于宿主和媒介种群动态、病毒传播和群体免疫。我们调整了我们的 WNV 模型，以适应明尼阿波利斯大都市区报告的鸟类、马和人类病例的每月总数。从这个过程中，我们估计疾病控制与预防中心报告的实际由 WNV 引起的死鸟比例约为 0.8%，而 7.3%的马病例和 10.7%的人类病例被报告。这与参考专家意见一致，即约 10%的马和人类病例有症状（其余 90%的无症状病例通常未报告）。尽管监测数据和现场观测的完整性有限，但观察到的时间序列中的所有主要高峰都被模拟捕捉到。观察到的时间序列与模拟时间序列之间的相关系数分别为死鸟 R=0.75，有症状马病例 R=0.96，人类神经侵袭性病例 R=0.86。
