Focus expansion and stability of the spread parameter estimate of the power law model for dispersal gradients
Focus expansion and stability of the spread parameter estimate of the power law model for dispersal gradients
复制标题
扩散梯度幂律模型扩散参数估计的焦点扩展和稳定性
作者：
P. Ojiambo;D. Gent;L. Mehra;David Christie;Roger Magarey
经验模型和机制模型表明，通过空中分散的接种物传播的病原体遵循幂律，导致分散的流行波。幂律模型的传播参数(b)是单位时间内流行病波阵面与初始焦点距离的指标，在有利于疾病传播的条件下，在大范围的空间尺度上，几种动植物疾病的传播参数(b)约为2。虽然疾病传播和流行病扩大可受到若干因素的影响，但尚未确定参数b在多个流行年中的稳定性。此外，预计最初流行区的大小与流行病的最终流行程度密切相关，但这种关系的稳定性也没有很好地确定。本文以2008年至2014年黄瓜霜霉病流行的实证数据为基础，采用将时间逻辑增长与扩散幂律函数相结合的疾病传播时空模型进行分析。最终流行范围从2012年的4.16 ×108 km2到2009年的6.44 ×108 km2。当前流行程度与4月底前后开始的最终流行区呈显著相关（P < 0.0332; 0.56 < R2 < 0.99），到7月流行季结束时，相关性单调递增至1.0。随着时间的推移，流行波前的位置呈指数增长，流行速度随距离呈线性增长。时间和空间回归模型的斜率在各个流行年份的变化范围约为2.5倍。在各个流行年份，b的估计值相差很大，从1.51到4.16不等。在幂律模型很好地描述数据的流行年份，我们观察到显著的b ×time（或距离）相互作用（P < 0.05）。这些结果表明，在多个流行年份，传播参数b可能不稳定。然而，对于遵循幂律扩散函数的经空中传播的病原体，b≈2可被认为是流行波阵面传播距离的下限。
Empirical and mechanistic modeling indicate that pathogens transmitted via aerially dispersed inoculum follow a power law, resulting in dispersive epidemic waves. The spread parameter (b) of the power law model, which is an indicator of the distance of the epidemic wave front from an initial focus per unit time, has been found to be approximately 2 for several animal and plant diseases over a wide range of spatial scales under conditions favorable for disease spread. Although disease spread and epidemic expansion can be influenced by several factors, the stability of the parameter b over multiple epidemic years has not been determined. Additionally, the size of the initial epidemic area is expected to be strongly related to the final epidemic extent for epidemics, but the stability of this relationship is also not well established. Here, empirical data of cucurbit downy mildew epidemics collected from 2008 to 2014 were analyzed using a spatio-temporal model of disease spread that incorporates logistic growth in time with a power law function for dispersal. Final epidemic extent ranged from 4.16 ×108 km2 in 2012 to 6.44 ×108 km2 in 2009. Current epidemic extent became significantly associated (P < 0.0332; 0.56 < R2 < 0.99) with final epidemic area beginning near the end of April, with the association increasing monotonically to 1.0 by the end of the epidemic season in July. The position of the epidemic wave-front became exponentially more distant with time, and epidemic velocity increased linearly with distance. Slopes from the temporal and spatial regression models varied with about a 2.5-fold range across epidemic years. Estimates of b varied substantially ranging from 1.51 to 4.16 across epidemic years. We observed a significant b ×time (or distance) interaction (P < 0.05) for epidemic years where data were well described by the power law model. These results suggest that the spread parameter b may not be stable over multiple epidemic years. However, b ≈ 2 may be considered the lower limit of the distance traveled by epidemic wave-fronts for aerially transmitted pathogens that follow a power law dispersal function.
由风传播的植物病原体引起的疾病传播的空间尺度关系。
DOI：
10.1890/es11-00281.1
发表时间：
2012
期刊：
Ecosphere (Washington, D.C)
影响因子：
--
作者：
Mundt,ChristopherC;Sackett,KathrynE
通讯作者：
Sackett,KathrynE
疾病暴发初期宿主的易感程度影响随后的疫情传播。
DOI：
10.1111/1365-2664.12326
发表时间：
2014
期刊：
The Journal of applied ecology
影响因子：
--
作者：
Severns,PaulM;Estep,LauraK;Sackett,KathrynE;Mundt,ChristopherC
通讯作者：
Mundt,ChristopherC