Abstract
SummaryBackgroundPredicting 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.MethodsIn 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.FindingsWe 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.InterpretationOur 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.FundingPaul G Allen Family Foundation, Bill & Melinda Gates Foundation, Wellcome Trust, UK Department for International Development.
Highlights
The Ebola virus disease outbreak, which centred in Guinea, Liberia, and Sierra Leone, was unprecedented both in terms of mortality and morbidity, as well as the extent to which the disease spread locally and internationally.[1]
To assess the ability of these pathogens to cause a widespread epidemic, we developed a framework that focuses on key transition points in a potential outbreak
Total population count evaluated at a 5 × 5 km resolution,[53] and the proportion of the total administrative unit population living within these locations, were aggregated to the admin 2 level[46] and standardised on a scale of 0–10.44 We evaluated a final stage 1 value by calculating an inverted geometric mean of these two population measures.[44]
Summary
The Ebola virus disease outbreak, which centred in Guinea, Liberia, and Sierra Leone, was unprecedented both in terms of mortality and morbidity, as well as the extent to which the disease spread locally and internationally.[1] The unanticipated cases of Ebola virus disease in regions previously considered non-endemic, coupled with inadequate infrastructure and susceptible, yet highly mobile populations, might have contributed to the outbreak infecting over 60 times more individuals than any previous Ebola virus disease outbreak.[2] As pathogens continue to emerge and spread into populations at-risk, a move from purely responsive activities to include proactive management of emerging infectious diseases is urgently needed.[3,4] The current paradigm of responding to these threats as and when they arise is expensive and unsustainable.[5] Initiatives such as the Coalition for Epidemic Preparedness Innovations and the US Global Health Security Agenda, with its renewed focus on achieving the International Health Regulations, have reinforced a need for a proactive approach to emerging infectious diseases.[6] there is great interest in the development of tools to help pre-empt such outbreaks and inform broad-scale health-system strengthening with respect to emerging infectious diseases,[7,8] and to establish the prioritisation of limited resources[9] and the optimal deployment of surveillance, preventive measures, and treatments
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