Institute for Health Metrics and Evaluation, University of Washington, Seattle, WA, USA.
Department of Zoology, University of Oxford, Oxford, UK; Harvard Medical School, Harvard University, Boston, MA, USA; Boston Children's Hospital, Boston, MA, USA.
Lancet. 2017 Dec 16;390(10113):2662-2672. doi: 10.1016/S0140-6736(17)32092-5. Epub 2017 Oct 12.
Predicting when and where pathogens will emerge is difficult, yet, as shown by the recent Ebola and Zika epidemics, effective and timely responses are key. It is therefore crucial to transition from reactive to proactive responses for these pathogens. To better identify priorities for outbreak mitigation and prevention, we developed a cohesive framework combining disparate methods and data sources, and assessed subnational pandemic potential for four viral haemorrhagic fevers in Africa, Crimean-Congo haemorrhagic fever, Ebola virus disease, Lassa fever, and Marburg virus disease.
In this multistage analysis, we quantified three stages underlying the potential of widespread viral haemorrhagic fever epidemics. Environmental suitability maps were used to define stage 1, index-case potential, which assesses populations at risk of infection due to spillover from zoonotic hosts or vectors, identifying where index cases could present. Stage 2, outbreak potential, iterates upon an existing framework, the Index for Risk Management, to measure potential for secondary spread in people within specific communities. For stage 3, epidemic potential, we combined local and international scale connectivity assessments with stage 2 to evaluate possible spread of local outbreaks nationally, regionally, and internationally.
We found epidemic potential to vary within Africa, with regions where viral haemorrhagic fever outbreaks have previously occurred (eg, western Africa) and areas currently considered non-endemic (eg, Cameroon and Ethiopia) both ranking highly. Tracking transitions between stages showed how an index case can escalate into a widespread epidemic in the absence of intervention (eg, Nigeria and Guinea). Our analysis showed Chad, Somalia, and South Sudan to be highly susceptible to any outbreak at subnational levels.
Our analysis provides a unified assessment of potential epidemic trajectories, with the aim of allowing national and international agencies to pre-emptively evaluate needs and target resources. Within each country, our framework identifies at-risk subnational locations in which to improve surveillance, diagnostic capabilities, and health systems in parallel with the design of policies for optimal responses at each stage. In conjunction with pandemic preparedness activities, assessments such as ours can identify regions where needs and provisions do not align, and thus should be targeted for future strengthening and support.
Paul G Allen Family Foundation, Bill & Melinda Gates Foundation, Wellcome Trust, UK Department for International Development.
预测病原体何时何地出现具有一定难度，然而，正如最近的埃博拉和寨卡疫情所表明的那样，及时有效的应对措施是关键。因此，对于这些病原体，从被动反应向主动反应转变至关重要。为了更好地确定减轻和预防疫情爆发的优先事项，我们开发了一个综合框架，结合了不同的方法和数据源，并评估了非洲四种病毒性出血热（克里米亚-刚果出血热、埃博拉病毒病、拉沙热和马尔堡病毒病）的次国家级大流行潜力。
在这一多阶段分析中，我们量化了广泛的病毒性出血热疫情潜力的三个阶段。使用环境适宜性图来定义第 1 阶段，即指标病例潜力，评估由于人畜共患病宿主或媒介的溢出而感染风险的人群，确定可能出现指标病例的地方。第 2 阶段，即疫情潜力，对现有框架——风险管理指标进行迭代，以衡量特定社区内人员的二次传播潜力。第 3 阶段，即流行潜力，我们将地方和国际规模的连通性评估与第 2 阶段相结合，以评估地方疫情在国家、地区和国际范围内的可能传播。
我们发现非洲内部的流行潜力存在差异，以前发生过病毒性出血热疫情的地区（如西非）和目前被认为是非疫区的地区（如喀麦隆和埃塞俄比亚）排名都很高。跟踪各阶段之间的转变表明，如果没有干预，一个指标病例可能会升级为广泛的疫情（如尼日利亚和几内亚）。我们的分析表明，乍得、索马里和南苏丹在次国家级层面极易受到任何疫情的影响。
我们的分析提供了对潜在疫情轨迹的统一评估，旨在使国家和国际机构能够预先评估需求并将资源集中在目标上。在每个国家内部，我们的框架确定了存在风险的次国家级地点，以便在平行于设计每个阶段的最佳应对政策的同时，改善监测、诊断能力和卫生系统。结合大流行准备活动，我们这样的评估可以确定需求和供应不匹配的地区，从而应该成为未来加强和支持的目标。
保罗·艾伦家族基金会、比尔及梅琳达·盖茨基金会、惠康信托基金会、英国国际发展部。
