Estimating the transmission potential of supercritical processes based on the final size distribution of minor outbreaks.
Estimating the transmission potential of supercritical processes based on the final size distribution of minor outbreaks.
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DOI：
10.1016/j.jtbi.2011.10.039
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发表时间：
2012-02-07
影响因子：
2
通讯作者：
Mode, Charles J.
中科院分区：
文献类型：
--
作者：
Nishiura, Hiroshi;Yan, Ping;Sleeman, Candace K.;Mode, Charles J.
关键词：
利用微小疫情的最终大小分布来估计超临界流行病过程的繁殖数量还有待考虑。我们使用了一个分支过程模型来推导出微小疫情的最终大小分布，假设复制次数大于1，并将该方法应用于肺鼠疫的最终大小数据。肺鼠疫是一种罕见的疾病，在空间有限的环境中只有一次有记录的重大流行。由于小爆发的最终大小分布需要用灭绝概率进行归一化，因此我们假设负二项后代分布的离散参数(K)是已知的，并检验了繁殖数对离散变化的敏感性。假设子代服从几何分布，k=1，则繁殖数估计为1.16(95%可信区间：0.97-1.38)。当k=2时，较小的离散度时，繁殖数的最大似然估计为1.14。这些估计与传播网络分析发表的结果一致，表明肺鼠疫在人与人之间传播的潜力不是很高。鉴于仅有少量暴发，通过直接计算后代数量不能充分评估传播潜力。由于没有大流行并不保证亚临界过程，所提出的方法允许我们保守地将来自小暴发的流行病数据视为超临界，并给出高于1的阈值估计。►即使对于超临界过程，可用数据也可能仅限于轻微爆发。假设R0和Gt；1，推导出微小疫情的►最终大小分布。►将所提出的方法用于估计肺鼠疫的R0。►仅给出较小的暴发数据，不能通过直接计算后代数量来充分估计R0。►轻微暴发数据需要通过亚临界和超临界假设进行评估。
Use of the final size distribution of minor outbreaks for the estimation of the reproduction numbers of supercritical epidemic processes has yet to be considered. We used a branching process model to derive the final size distribution of minor outbreaks, assuming a reproduction number above unity, and applying the method to final size data for pneumonic plague. Pneumonic plague is a rare disease with only one documented major epidemic in a spatially limited setting. Because the final size distribution of a minor outbreak needs to be normalized by the probability of extinction, we assume that the dispersion parameter (k) of the negative-binomial offspring distribution is known, and examine the sensitivity of the reproduction number to variation in dispersion. Assuming a geometric offspring distribution with k=1, the reproduction number was estimated at 1.16 (95% confidence interval: 0.97–1.38). When less dispersed with k=2, the maximum likelihood estimate of the reproduction number was 1.14. These estimates agreed with those published from transmission network analysis, indicating that the human-to-human transmission potential of the pneumonic plague is not very high. Given only minor outbreaks, transmission potential is not sufficiently assessed by directly counting the number of offspring. Since the absence of a major epidemic does not guarantee a subcritical process, the proposed method allows us to conservatively regard epidemic data from minor outbreaks as supercritical, and yield estimates of threshold values above unity. ► Even for supercritical process, the available data may be limited to minor outbreaks. ► Final size distribution of minor outbreaks is derived assuming R0>1. ► The proposed method was used to estimate R0 of pneumonic plague. ► Given only minor outbreak data, estimation of R0 is not sufficiently achieved by directly counting the number of offspring. ► Minor outbreak data need to be assessed by both subcritical and supercritical assumptions.
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