Department of Disease Control, School of Veterinary Medicine, University of Zambia, Lusaka, Zambia.
School of Health Sciences, University of Zambia, Lusaka, Zambia.
PLoS Negl Trop Dis. 2020 Nov 9;14(11):e0008811. doi: 10.1371/journal.pntd.0008811. eCollection 2020 Nov.
Plague is a re-emerging flea-borne infectious disease of global importance and in recent years, Zambia has periodically experienced increased incidence of outbreaks of this disease. However, there are currently no studies in the country that provide a quantitative assessment of the ability of the disease to spread during these outbreaks. This limits our understanding of the epidemiology of the disease especially for planning and implementing quantifiable and cost-effective control measures. To fill this gap, the basic reproduction number, R0, for bubonic plague was estimated in this study, using data from the 2015 Nyimba district outbreak, in the Eastern province of Zambia. R0 is the average number of secondary infections arising from a single infectious individual during their infectious period in an entirely susceptible population.
METHODOLOGY/PRINCIPAL FINDINGS: Secondary epidemic data for the most recent 2015 Nyimba district bubonic plague outbreak in Zambia was analyzed. R0 was estimated as a function of the average epidemic doubling time based on the initial exponential growth rate of the outbreak and the average infectious period for bubonic plague. R0 was estimated to range between 1.5599 [95% CI: 1.382-1.7378] and 1.9332 [95% CI: 1.6366-2.2297], with average of 1.7465 [95% CI: 1.5093-1.9838]. Further, an SIR deterministic mathematical model was derived for this infection and this estimated R0 to be between 1.4 to 1.5, which was within the range estimated above.
CONCLUSIONS/SIGNIFICANCE: This estimated R0 for bubonic plague is an indication that each bubonic plague case can typically give rise to almost two new cases during these outbreaks. This R0 estimate can now be used to quantitatively analyze and plan measurable interventions against future plague outbreaks in Zambia.
鼠疫是一种具有全球重要性的重新出现的跳蚤传播传染病，近年来，赞比亚周期性地经历了这种疾病爆发的发病率增加。然而，目前该国没有研究提供定量评估疾病在这些爆发期间传播能力的研究。这限制了我们对疾病流行病学的理解，特别是在规划和实施可量化和具有成本效益的控制措施方面。为了填补这一空白，本研究使用来自赞比亚东部恩耶马地区 2015 年爆发的数据，估计了腺鼠疫的基本繁殖数 R0。R0 是在完全易感人群中，单个传染性个体在其传染性期间产生的二次感染的平均数量。
方法/主要发现：分析了赞比亚最近一次 2015 年恩耶马地区腺鼠疫爆发的二级疫情数据。根据疫情的初始指数增长率和腺鼠疫的平均传染期，R0 被估计为平均疫情倍增时间的函数。R0 的估计范围在 1.5599[95%CI:1.382-1.7378]和 1.9332[95%CI:1.6366-2.2297]之间，平均值为 1.7465[95%CI:1.5093-1.9838]。此外，还为这种感染推导出了一个 SIR 确定性数学模型，该模型估计的 R0 介于 1.4 到 1.5 之间，在上述估计范围内。
结论/意义：腺鼠疫的这个估计 R0 表明，在这些爆发期间，每个腺鼠疫病例通常会产生近两个新病例。这个 R0 估计现在可以用于定量分析和规划针对赞比亚未来鼠疫爆发的可衡量干预措施。
