Ebola Surveillance - Guinea, Liberia, and Sierra Leone

Representations of an Ebola 'outbreak' through Story Technologies

BACKGROUND

Attempts to understand biosocial phenomena using scientific methods are often presented as value-neutral and objective; however, when used to reduce the complexity of open systems such as epidemics, these forms of inquiry necessarily entail normative considerations and are therefore fashioned by political worldviews (ideologies). From the standpoint of poststructural theory, the character of these representations is at most limited and partial. In addition, these modes of representation (as stories) do work (as technologies) in the service of, or in resistance to, power.

METHODS

We focus on a single Ebola case cluster from the 2013-2016 outbreak in West Africa and examine how different disciplinary forms of knowledge production (including outbreak forecasting, active epidemiological surveillance, post-outbreak serosurveys, political economic analyses, and ethnography) function as Story Technologies. We then explore how these technologies are used to curate 'data,' analysing the erasures, values, and imperatives evoked by each.

RESULTS

We call attention to the instrumental-in addition to the descriptive-role Story Technologies play in ordering contingencies and establishing relationships in the wake of health crises.

DISCUSSION

By connecting each type of knowledge production with the systems of power it reinforces or disrupts, we illustrate how Story Technologies do ideological work. These findings encourage research from pluriversal perspectives and advocacy for measures that promote more inclusive modes of knowledge production.

Post-epidemic health system recovery: A comparative case study analysis of routine immunization programs in the Republics of Haiti and Liberia

Large-scale epidemics in resource-constrained settings disrupt delivery of core health services, such as routine immunization. Rebuilding and strengthening routine immunization programs following epidemics is an essential step toward improving vaccine equity and averting future outbreaks. We performed a comparative case study analysis of routine immunization program recovery in Liberia and Haiti following the 2014-16 West Africa Ebola epidemic and 2010s cholera epidemic, respectively. First, we triangulated data between the peer-reviewed and grey literature; in-depth key informant interviews with subject matter experts; and quantitative metrics of population health and health system functioning. We used these data to construct thick descriptive narratives for each case. Finally, we performed a cross-case comparison by applying a thematic matrix based on the Essential Public Health Services framework to each case narrative. In Liberia, post-Ebola routine immunization coverage surpassed pre-epidemic levels, a feat attributable to investments in surveillance, comprehensive risk communication, robust political support for and leadership around immunization, and strong public-sector recovery planning. Recovery efforts in Haiti were fragmented across a broad range of non-governmental agencies. Limitations in funding, workforce development, and community engagement further impeded vaccine uptake. Consequently, Haiti reported significant disparities in subnational immunization coverage following the epidemic. This study suggests that embedding in-country expertise within outbreak response structures, respecting governmental autonomy, aligning post-epidemic recovery plans and policies, and integrating outbreak response assets into robust systems of primary care contribute to higher, more equitable levels of routine immunization coverage in resource-constrained settings recovering from epidemics.

A sequential test for assessing the effectiveness of response strategies during an emerging epidemic

In epidemiology, the fatality rate is an important indicator of disease severity and has been used to evaluate the effects of new treatments. During an emerging epidemic with limited resources, monitoring the changes in fatality rate can also provide signals on the evaluation of government policies and healthcare quality, which helps to guide public health decision. A statistical test is developed in this paper to detect changes in fatality rate over time during the course of an emerging infectious disease. A major advantage of the proposed test is that it only requires the regularly reported numbers of deaths and recoveries, which meets the actual need as detailed surveillance data are hard to collect during the course of an emerging epidemic especially the deadly infectious diseases with large magnitude. In addition, with the sequential testing procedure, the effective measures can be detected at the earliest possible time to provide guidance to policymakers for swift action. Simulation studies showed that the proposed test performs well and is sensitive in picking up changes in the fatality rate. The test is applied to the 2014-2016 Ebola outbreak in Sierra Leone for illustration.

Geospatial clustering and correlates of deaths during the Ebola outbreak in Liberia: a Bayesian geoadditive semiparametric analysis of nationally representative cross-sectional survey data

OBJECTIVE

To investigate the extent of geospatial clustering of reported deaths during the Ebola outbreak in Liberia and the covariates associated with the observed clustering.

DESIGN

Cross-sectional study.

PARTICIPANTS

Male and female respondents from the 2019-2020 Liberia Demographic and Health Survey. The analysis covered 11 928 (women=7854 and men=4074) respondents for whom complete data were available.

OUTCOME MEASURES

The outcome variable was the death of a household member or relative during the Ebola outbreak in Liberia, coded 1 if the respondent reported death and 0 otherwise.

METHODS

We applied the Bayesian geoadditive semiparametric regression to examine the extent of geospatial clustering of deaths at the district-level and community-level development and socioeconomic factors associated with the observed clustering.

RESULTS

Almost a quarter (24.8%) of all respondents reported the death of a household member or relative during the Ebola outbreak. The results show that deaths were clustered within districts in six (Grand Cape Mount, Bomi, Monsterrado, Margibi, Gbarpolu and Lofa) of the 15 counties in Liberia. Districts with high death clustering were all near or shared borders with Sierra Leone and Guinea. The community-level development indicators (global human footprint, gross cell production and population density) had a non-linear associative effect with the observed spatial clustering. Also, respondents' characteristics (respondent's age (non-linear effect), educational attainment and urban-rural place of residence) were associated with the observed clustering. The results show that death clustering during outbreaks was constrained to poor settings and impacts areas of moderate and high socioeconomic development.

CONCLUSION

Reported deaths during the Ebola outbreak in Liberia were not randomly distributed at the district level but clustered. The findings highlight the need to identify at-risk populations during epidemics and respond with the needed interventions to save lives.

Implementing a DHIS2 Ebola virus disease module during the 2021 Guinea Ebola outbreak

In 2017, the national agency for health security (L'Agence Nationale de Sécurité Sanitaire-ANSS) in Guinea implemented the District Health Information Software (DHIS2) as the Ministry of Health national surveillance system to capture and report aggregate disease data. During 2019, the ANSS started using DHIS2 Tracker to collect case-based (individual-level) data for epidemic-prone diseases. In 2020, the capability was expanded, and it was used during the COVID-19 pandemic to capture data relevant to the COVID-19 response. When an Ebola virus disease (EVD) outbreak was announced in February 2021, the Tracker module was updated, and enhanced functionalities were developed to meet the needs for the emerging epidemic. This novel EVD module has components to capture information on cases, contacts, alerts, laboratory and vaccinations and provides a centralised site for all EVD outbreak data. It has since been expanded for use with future viral haemorrhagic fever outbreaks.

The role of health systems for health security: a scoping review revealing the need for improved conceptual and practical linkages

BACKGROUND

Practical links between health systems and health security are historically prevalent, but the conceptual links between these fields remain under explored, with little on health system strengthening. The need to address this gap gains relevance in light of the COVID-19 pandemic as it demonstrated a crucial relationship between health system capacities and effective health security response. Acknowledging the importance of developing stronger and more resilient health systems globally for health emergency preparedness, the WHO developed a Health Systems for Health Security framework that aims to promote a common understanding of what health systems for health security entails whilst identifying key capacities required.

METHODS/ RESULTS

To further explore and analyse the conceptual and practical links between health systems and health security within the peer reviewed literature, a rapid scoping review was carried out to provide an overview of the type, extent and quantity of research available. Studies were included if they had been peer-reviewed and were published in English (seven databases 2000 to 2020). 343 articles were identified, of those 204 discussed health systems and health security (high and medium relevance), 101 discussed just health systems and 47 discussed only health security (low relevance). Within the high and medium relevance articles, several concepts emerged, including the prioritization of health security over health systems, the tendency to treat health security as exceptionalism focusing on acute health emergencies, and a conceptualisation of security as 'state security' not 'human security' or population health.

CONCLUSION

Examples of literature exploring links between health systems and health security are provided. We also present recommendations for further research, offering several investments and/or programmes that could reliably lead to maximal gains from both a health system and a health security perspective, and why these should be explored further. This paper could help researchers and funders when deciding upon the scope, nature and design of future research in this area. Additionally, the paper legitimises the necessity of the Health Systems for Health Security framework, with the findings of this paper providing useful insights and evidentiary examples for effective implementation of the framework.

Social Contacts and Transmission of COVID-19 in British Columbia, Canada

Background

Close-contact rates are thought to be a driving force behind the transmission of many infectious respiratory diseases. Yet, contact rates and their relation to transmission and the impact of control measures, are seldom quantified. We quantify the response of contact rates, reported cases and transmission of COVID-19, to public health contact-restriction orders, and examine the associations among these three variables in the province of British Columbia, Canada.

Methods

We derived time series data for contact rates, daily cases and transmission of COVID-19 from a social contacts survey, reported case counts and by fitting a transmission model to reported cases, respectively. We used segmented regression to investigate impacts of public health orders; Pearson correlation to determine associations between contact rates and transmission; and vector autoregressive modeling to quantify lagged associations between contacts rates, daily cases, and transmission.

Results

Declines in contact rates and transmission occurred concurrently with the announcement of public health orders, whereas declines in cases showed a reporting delay of about 2 weeks. Contact rates were a significant driver of COVID-19 and explained roughly 19 and 20% of the variation in new cases and transmission, respectively. Interestingly, increases in COVID-19 transmission and cases were followed by reduced contact rates: overall, daily cases explained about 10% of the variation in subsequent contact rates.

Conclusion

We showed that close-contact rates were a significant time-series driver of transmission and ultimately of reported cases of COVID-19 in British Columbia, Canada and that they varied in response to public health orders. Our results also suggest possible behavioral feedback, by which increased reported cases lead to reduced subsequent contact rates. Our findings help to explain and validate the commonly assumed, but rarely measured, response of close contact rates to public health guidelines and their impact on the dynamics of infectious diseases.

Seizing the moment: now is the time for integrated global surveillance of antimicrobial resistance in wastewater environments

Antimicrobial resistance (AMR) is a growing global health threat that requires coordinated action across One Health sectors (humans, animals, environment) to stem its spread. Environmental surveillance of AMR is largely behind the curve in current One Health surveillance programs, but recent momentum in the establishment of infrastructure for monitoring of the SARS-CoV-2 virus in sewage provides an impetus for analogous AMR monitoring. Simultaneous advances in research have identified striking trends in various AMR measures in wastewater and other impacted environments across global transects. Methodologies for tracking AMR, including metagenomics, are rapidly advancing, but need to be standardized and made modular for access by LMICs, while also developing systems for sample archiving and data sharing. Such efforts will help optimize effective global AMR policy.

Perceived sources of occupational burn-out and embitterment among front-line health workers for COVID-19 control in Gyeonggi province, South Korea: a qualitative study

Objectives

Front-line health workers (FHWs) for COVID-19 control in South Korea have implemented a labour-intensive contact tracing programme, which places them at high risk for mental health problems. However, a few studies have examined mental health conditions in this population. We employed a qualitative approach to understand the factors perceived as causes of burn-out and embitterment among temporary FHWs to provide recommendations for supporting the workforce.

Methods

We recruited 20 FHWs to participate in semistructured focus group interviews through purposive sampling. The sample size was determined on the basis of data saturation. We collected data from October to November 2020, audiorecording and transcribing the interviews. Data analysis was conducted manually, applying the principles of grounded theory.

Results

Five levels of perceived sources of occupational burn-out and embitterment emerged. FHWs showed considerable mistrust of patients and faced ethical dilemmas in accessing and disclosing personal information. Poor collaboration with community health centre workers and interested parties as well as inadequate organisational support aggravated their conditions. Lack of social recognition and employment instability also presented challenges for FHWs’ mental health.

Conclusions

The current pandemic response system imposes great moral and emotional burdens on the workforce, prompting the need for initiatives to safeguard the values and needs of those who represent the backbone of the system. This study suggests that multilevel strategies, including providing organisational support and establishing contingency plans for workforce management and resource distribution, may improve FHWs’ mental health outcomes as well as the health system for emergency preparedness.

The first eight months of COVID-19 pandemic in three West African countries: leveraging lessons learned from responses to the 2014-2016 Ebola virus disease outbreak

Experience gained from responding to major outbreaks may have influenced the early coronavirus disease-2019 (COVID-19) pandemic response in several countries across Africa. We retrospectively assessed whether Guinea, Liberia and Sierra Leone, the three West African countries at the epicentre of the 2014–2016 Ebola virus disease outbreak, leveraged the lessons learned in responding to COVID-19 following the World Health Organization's (WHO) declaration of a public health emergency of international concern (PHEIC). We found relatively lower incidence rates across the three countries compared to many parts of the globe. Time to case reporting and laboratory confirmation also varied, with Guinea and Liberia reporting significant delays compared to Sierra Leone. Most of the selected readiness measures were instituted before confirmation of the first case and response measures were initiated rapidly after the outbreak confirmation. We conclude that the rapid readiness and response measures instituted by the three countries can be attributed to their lessons learned from the devastating Ebola outbreak, although persistent health systems weaknesses and the unique nature of COVID-19 continue to challenge control efforts.

Global Research Activity on Health System Preparedness Against Viral Infectious Disease Outbreaks

OBJECTIVE

The present study aimed to give an overview of research publications on health system preparedness against viral infectious disease outbreaks.

METHODS

A bibliometric method was implemented from 2001 to 2020. The studied pathogens were dengue, Ebola, influenza, Zika, Middle East respiratory syndrome (MERS), Severe acute respiratory syndrome (SARS), and coronavirus disease 2019 (COVID-19).

RESULTS

The search query returned 501 documents. The growth of publications showed a sharp peak in 2020 for COVID-19 and 3 small peaks in 2006, 2009, and 2015 for SARS, influenza, and Ebola, respectively. Of the retrieved documents, 208 (41.5%) were on influenza, 164 (32.7%) were on COVID-19, and 83 (16.6%) were on Ebola. Countries in the region of the Americas (n = 221; 44.1%) returned the majority of the documents, while countries in Latin America and the African region returned the least. The United States (n = 197; 39.3%) had a leading role in this field. The US Centers for Disease Control and Prevention (n = 51; 10.2%) ranked first, followed by the Johns Hopkins University (n = 16; 3.2%). The Disaster Medicine and Public Health Preparedness journal (n = 21; 4.2%) ranked first. International research collaboration was relatively inadequate.

CONCLUSIONS

Research on preparedness against infectious diseases was episodic. Research collaboration needs to be prioritized for countries with a history of fatal outbreaks.

International Wildlife Trafficking: A perspective on the challenges and potential forensic genetics solutions

International wildlife trafficking (IWT) is a thriving and pervasive illegal enterprise that adversely affects modern societies. Yet, despite being globally recognized as a threat to biodiversity, national security, economy, and biosecurity, IWT remains largely unabated and is proliferating at an alarming rate. The increase in IWT is generally attributed to a lack of prioritization to curb wildlife crime through legal and scientific infrastructure. This review: (1) lays out the damaging scope and influence of IWT; (2) discusses the potential of DNA marker systems, barcodes, and emerging molecular technologies, such as long-read portable sequencing, to facilitate rapid, in situ identification of species and individuals; and (3) encourages initiatives that promote quality and innovation. Interdisciplinary collaboration promises to be one of the most effective ways forward to surmounting the complex scientific and legal challenges posed by IWT.

Building the Sierra Leone Ebola Database: organization and characteristics of data systematically collected during 2014-2015 Ebola epidemic

PURPOSE

During the 2014-2016 Ebola outbreak in West Africa, the Sierra Leone Ministry of Health and Sanitation (MoHS), the US Centers for Disease Control and Prevention, and responding partners under the coordination of the National Ebola Response Center (NERC) and the MoHS's Emergency Operation Center (EOC) systematically recorded information from the 117 Call Center system and district alert phone lines, case investigations, laboratory sample testing, clinical management, and safe and dignified burial records. Since 2017, CDC assisted MoHS in building and managing the Sierra Leone Ebola Database (SLED) to consolidate these major data sources. The primary objectives of the project were helping families to identify the location of graves of their loved ones who died at the time of the Ebola epidemic through the SLED Family Reunification Program and creating a data source for epidemiological research. The objective of this paper is to describe the process of consolidating epidemic records into a useful and accessible data collection and to summarize data characteristics, strength, and limitations of this unique information source for public health research.

METHODS

Because of the unprecedented conditions during the epidemic, most of the records collected from responding organizations required extensive processing before they could be used as a data source for research or the humanitarian purpose of locating burial sites. This process required understanding how the data were collected and used during the outbreak. To manage the complexity of processing the data obtained from various sources, the Sierra Leone Ebola Database (SLED) Team used an organizational strategy that allowed tracking of the data provenance and lifecycle.

RESULTS

The SLED project brought raw data into one consolidated data collection. It provides researchers with secure and ethical access to the SLED data and serves as a basis for the research capacity building in Sierra Leone. The SLED Family Reunification Program allowed Sierra Leonean families to identify location of the graves of loved ones who died during the Ebola epidemic.

CONCLUSIONS

The SLED project consolidated and utilized epidemic data recorded during the Sierra Leone Ebola Virus Disease outbreak that were collected and contributed to SLED by national and international organizations. This project has provided a foundation for developing a method of ethical and secure SLED data access while preserving the host nation's data ownership. SLED serves as a data source for the SLED Family Reunification Program and for epidemiological research. It presents an opportunity for building research capacity in Sierra Leone and provides a foundation for developing a relational database. Large outbreak data systems such as SLED provide a unique opportunity for researchers to improve responses to epidemics and indicate the need to include data management preparedness in the plans for emergency response.

COVID-19 preparedness at health facilities and community service points serving people living with HIV in Sierra Leone

After a decade of civil war and the 2014–2016 West African Ebola outbreak, Sierra Leone now faces the COVID-19 pandemic with a fragile health system. As was demonstrated during Ebola, preparedness is key to limiting a health crisis’ spread and impact on health systems and ensuring continued care for vulnerable populations including people living with HIV (PLHIV). To assess COVID-19 preparedness and inform interventions to ensure continuity of HIV services at health facilities (HFs) and community service points (CSPs), we conducted site readiness assessments in Freetown, the epicenter of COVID-19 in Sierra Leone. Data were collected at nine high-volume HIV HFs and seven CSPs in April 2020, a month after COVID-19 was declared a pandemic. CSPs comprised three community drop-in centers providing HIV counseling and testing services as well as HIV prevention services (e.g., condoms and lubricants) for key and priority populations and four community-based support groups serving PLHIV. At the time of assessment, CSPs did not provide antiretroviral therapy (ART) but were considered potential sites for expansion of differentiated service delivery (DSD)—a client-centered approach to HIV care—in the context of COVID-19. Overall, 5/9 HFs had trained staff on use of personal protective equipment (PPE) and prevention of COVID-19 transmission. Most had access to masks (5/9) and gloves (7/9) for management of suspected/confirmed COVID-19 cases, and 4/9 HFs had triage procedures for isolation of suspected cases. Conversely, few CSPs had access to masks (2/7) or gloves (2/7) and no staff were trained on PPE use or COVID-19 transmission. 7/9 HFs had adequate ART stock for multi-month dispensing though few had procedures for (3/9) or had trained staff in providing DSD (2/9). Among CSPs where measures were applicable, 2/4 had procedures for DSD, 1/3 had staff trained on DSD and none had adequate ART stock. Identification of gaps in COVID-19 preparedness is a critical step in providing support for infection control and modified service delivery. Findings from this assessment highlight gaps in COVID-19 preparedness measures at sites supporting PLHIV in Sierra Leone and indicate CSPs may require intensive supervision and training to ensure HIV services are uninterrupted while minimizing COVID-19 risk, especially if used as sites to scale up DSD.

Antibody affinity as a driver of signal generation in a paper-based immunoassay for Ebola virus surveillance

During epidemics, such as the frequent and devastating Ebola virus outbreaks that have historically plagued regions of Africa, serological surveillance efforts are critical for viral containment and the development of effective antiviral therapeutics. Antibody serology can also be used retrospectively for population-level surveillance to provide a more complete estimate of total infections. Ebola surveillance efforts rely on enzyme-linked immunosorbent assays (ELISAs), which restrict testing to laboratories and are not adaptable for use in resource-limited settings. In this manuscript, we describe a paper-based immunoassay capable of detecting anti-Ebola IgG using Ebola virus envelope glycoprotein ectodomain (GP) as the affinity reagent. We evaluated seven monoclonal antibodies (mAbs) against GP—KZ52, 13C6, 4G7, 2G4, c6D8, 13F6, and 4F3—to elucidate the impact of binding affinity and binding epitope on assay performance and, ultimately, result interpretation. We used biolayer interferometry to characterize the binding of each antibody to GP before assessing their performance in our paper-based device. Binding affinity (K_D) and on rate (k_on) were major factors influencing the sensitivity of the paper-based immunoassay. mAbs with the best K_D (3–25 nM) exhibited the lowest limits of detection (ca. μg mL⁻¹), while mAbs with K_D > 25 nM were undetectable in our device. Additionally, and most surprisingly, we determined that observed signals in paper devices were directly proportional to k_on. These results highlight the importance of ensuring that the quality of recognition reagents is sufficient to support desired assay performance and suggest that the strength of an individual’s immune response can impact the interpretation of assay results.

Optimizing Pandemic Preparedness and Response Through Health Information Systems: Lessons Learned From Ebola to COVID-19

Strengthening health systems and maintaining essential service delivery during health emergencies response is critical for early detection and diagnosis, prompt treatment, and effective control of pandemics, including the novel coronavirus disease 2019 (COVID-19). Health information systems (HIS) developed during recent Ebola outbreaks in West Africa and the Democratic Republic of the Congo (DRC) provided opportunities to collect, analyze, and distribute data to inform both day-to-day and long-term policy decisions on outbreak preparedness. As COVID-19 continues to sweep across the globe, HIS and related technological advancements remain vital for effective and sustained data sharing, contact tracing, mapping and monitoring, community risk sensitization and engagement, preventive education, and timely preparedness and response activities. In reviewing literature of how HIS could have further supported mitigation of these Ebola outbreaks and the ongoing COVID-19 pandemic, 3 key areas were identified: governance and coordination, health systems infrastructure and resources, and community engagement. In this concept study, we outline scalable HIS lessons from recent Ebola outbreaks and early COVID-19 responses along these 3 domains, synthesizing recommendations to offer clear, evidence-based approaches on how to leverage HIS to strengthen the current pandemic response and foster community health systems resilience moving forward.

A Modified Case Definition to Facilitate Essential Hospital Care During Ebola Outbreaks

During the late phase of the large West-African Ebola virus disease (EVD) outbreak, the majority of patients were cared for in designated treatment centers. However, the preexisting healthcare infrastructure was already overwhelmed by the outbreak. This had a huge impact on other, non-EVD-related diseases, causing an unprecedented increase in morbidity and mortality, which most likely exceeded the toll due to EVD directly. Consequently, a crucial question is how to provide appropriate healthcare and safeguard functionality of a healthcare system that also serves patients not suspected or diagnosed to have EVD. Here, we report on the Lion Heart Medical Center's experience in Sierra Leone and note that a case definition of Ebola that is broader than those commonly applied may be better suited when it is necessary to identify atypically presenting, pauci-symptomatic cases.

Neurological, Cognitive, and Psychological Findings Among Survivors of Ebola Virus Disease From the 1995 Ebola Outbreak in Kikwit, Democratic Republic of Congo: A Cross-sectional Study

Background

Clinical sequelae of Ebola virus disease (EVD) have not been described more than 3 years postoutbreak. We examined survivors and close contacts from the 1995 Ebola outbreak in Kikwit, Democratic Republic of Congo (DRC), and determined prevalence of abnormal neurological, cognitive, and psychological findings and their association with EVD survivorship.

Methods

From August to September 2017, we conducted a cross-sectional study in Kikwit, DRC. Over 2 decades after the EVD outbreak, we recruited EVD survivors and close contacts from the outbreak to undergo physical examination and culturally adapted versions of the Folstein mini-mental status exam (MMSE) and Goldberg anxiety and depression scale (GADS). We estimated the strength of relationships between EVD survivorship and health outcomes using linear regression models by comparing survivors versus close contacts, adjusting for age, sex, educational level, marital status, and healthcare worker status.

Results

We enrolled 20 EVD survivors and 187 close contacts. Among the 20 EVD survivors, 4 (20%) reported at least 1 abnormal neurological symptom, and 3 (15%) had an abnormal neurological examination. Among the 187 close contacts, 14 (11%) reported at least 1 abnormal neurologic symptom, and 9 (5%) had an abnormal neurological examination. EVD survivors had lower mean MMSE and higher mean GADS scores as compared to close contacts (MMSE: adjusted coefficient: −1.85; 95% confidence interval [CI]: −3.63, −0.07; GADS: adjusted coefficient: 3.91; 95% CI: 1.76, 6.04).

Conclusions

EVD survivors can have lower cognitive scores and more symptoms of depression and anxiety than close contacts more than 2 decades after Ebola virus outbreaks.

Case Fatality Ratio Estimates for the 2013-2016 West African Ebola Epidemic: Application of Boosted Regression Trees for Imputation

BACKGROUND

The 2013-2016 West African Ebola epidemic has been the largest to date with >11 000 deaths in the affected countries. The data collected have provided more insight into the case fatality ratio (CFR) and how it varies with age and other characteristics. However, the accuracy and precision of the naive CFR remain limited because 44% of survival outcomes were unreported.

METHODS

Using a boosted regression tree model, we imputed survival outcomes (ie, survival or death) when unreported, corrected for model imperfection to estimate the CFR without imputation, with imputation, and adjusted with imputation. The method allowed us to further identify and explore relevant clinical and demographic predictors of the CFR.

RESULTS

The out-of-sample performance (95% confidence interval [CI]) of our model was good: sensitivity, 69.7% (52.5-75.6%); specificity, 69.8% (54.1-75.6%); percentage correctly classified, 69.9% (53.7-75.5%); and area under the receiver operating characteristic curve, 76.0% (56.8-82.1%). The adjusted CFR estimates (95% CI) for the 2013-2016 West African epidemic were 82.8% (45.6-85.6%) overall and 89.1% (40.8-91.6%), 65.6% (61.3-69.6%), and 79.2% (45.4-84.1%) for Sierra Leone, Guinea, and Liberia, respectively. We found that district, hospitalisation status, age, case classification, and quarter (date of case reporting aggregated at three-month intervals) explained 93.6% of the variance in the naive CFR.

CONCLUSIONS

The adjusted CFR estimates improved the naive CFR estimates obtained without imputation and were more representative. Used in conjunction with other resources, adjusted estimates will inform public health contingency planning for future Ebola epidemics, and help better allocate resources and evaluate the effectiveness of future inventions.

Ensuring ethical data access: the Sierra Leone Ebola Database (SLED) model

PURPOSE

Organizations responding to the 2014-2016 Ebola epidemic in Sierra Leone collected information from multiple sources and kept it in separate databases, including distinct data systems for Ebola hot line calls, patient information collected by field surveillance officers, laboratory testing results, clinical information from Ebola treatment and isolation facilities, and burial team records.

METHODS

After the conclusion of the epidemic, the Sierra Leone Ministry of Health and Sanitation and the U.S. Centers for Disease Control and Prevention partnered to collect these disparate records and consolidate them in the Sierra Leone Ebola Database.

RESULTS

The Sierra Leone Ebola Database data are providing a lasting resource for postepidemic data analysis and epidemiologic research, including identifying best strategies in outbreak response, and are used to help families locate the graves of family members who died during the epidemic.

CONCLUSION

This report describes the Ministry of Health and Sanitation and Centers for Disease Control and Prevention processes to safeguard Ebola records while making the data available for public health research.

Quality of age data in the Sierra Leone Ebola database

Introduction

While it is suspected that some ages were misreported during the 2014-2016 West African Ebola outbreak, an analysis examining age data quality has not been conducted. The study objective was to examine age heaping and terminal digit preference as indicators for quality of age data collected in the Sierra Leone Ebola Database (SLED).

Methods

Age data quality for adult patients was analyzed within SLED for the Viral Hemorrhagic Fever (VHF) database and the laboratory testing dataset by calculating Whipple´s index and Myers´s blended index, stratified by sex and region.

Results

Age data quality was low in both the VHF database (Whipple´s index for the 5-year range, 229.2) and the laboratory testing dataset (Whipple´s index for the 5-year range, 236.4). Age was reported more accurately in the Western Area and least accurately in the Eastern Province. Age data for females were less accurate than for males.

Conclusion

Age data quality was low in adult patients during the 2014-2016 Ebola outbreak in Sierra Leone, which may reduce its use as an identifying or stratifying variable. These findings inform future analyses using this database and describe a phenomenon that has relevance in data collection methods and analyses for future outbreaks in developing countries.

Spatiotemporal variability in case fatality ratios for the 2013-2016 Ebola epidemic in West Africa

BACKGROUND

For the 2013-2016 Ebola epidemic in West Africa, the largest Ebola virus disease (EVD) epidemic to date, we aim to analyse the patient mix in detail to characterise key sources of spatiotemporal heterogeneity in the case fatality ratios (CFR).

METHODS

We applied a non-parametric Boosted Regression Trees (BRT) imputation approach for patients with missing survival outcomes and adjusted for model imperfection. Semivariogram analysis and kriging were used to investigate spatiotemporal heterogeneities.

RESULTS

CFR estimates varied significantly between districts and over time over the course of the epidemic. BRT modelling accounted for most of the spatiotemporal variation and interactions in CFR, but moderate spatial autocorrelation remained for distances up to approximately 90 km. Combining district-level CFR estimates and kriged district-level residuals provided the best linear unbiased predicted map of CFR accounting for the both explained and unexplained spatial variation. Temporal autocorrelation was not observed in the district-level residuals from the BRT estimates.

CONCLUSIONS

This study provides new insight into the epidemiology of the 2013-2016 West African Ebola epidemic with a view of informing future public health contingency planning, resource allocation and impact assessment. The analytical framework developed in this analysis, coupled with key domain knowledge, could be deployed in real time to support the response to ongoing and future outbreaks.

Costs and benefits of early response in the Ebola virus disease outbreak in Sierra Leone

Background

The 2014–2016 Ebola virus disease (EVD) outbreak in West Africa was the largest EVD outbreak recorded, which has triggered calls for investments that would facilitate an even earlier response. This study aims to estimate the costs and health effects of earlier interventions in Sierra Leone.

Methods

A deterministic and a stochastic compartment model describing the EVD outbreak was estimated using a variety of data sources. Costs and Disability-Adjusted Life Years were used to estimate and compare scenarios of earlier interventions.

Results

Four weeks earlier interventions would have averted 10,257 (IQR 4353–18,813) cases and 8835 (IQR 3766–16,316) deaths. This implies 456 (IQR 194–841) thousand DALYs and 203 (IQR 87–374) million $US saved. The greatest losses occurred outside the healthcare sector.

Conclusions

Earlier response in an Ebola outbreak saves lives and costs. Investments in healthcare system facilitating such responses are needed and can offer good value for money.

Infectious disease outbreaks in the African region: overview of events reported to the World Health Organization in 2018

The WHO African region is characterised by the largest infectious disease burden in the world. We conducted a retrospective descriptive analysis using records of all infectious disease outbreaks formally reported to the WHO in 2018 by Member States of the African region. We analysed the spatio-temporal distribution, the notification delay as well as the morbidity and mortality associated with these outbreaks. In 2018, 96 new disease outbreaks were reported across 36 of the 47 Member States. The most commonly reported disease outbreak was cholera which accounted for 20.8% (n = 20) of all events, followed by measles (n = 11, 11.5%) and Yellow fever (n = 7, 7.3%). About a quarter of the outbreaks (n = 23) were reported following signals detected through media monitoring conducted at the WHO regional office for Africa. The median delay between the disease onset and WHO notification was 16 days (range: 0-184). A total of 107 167 people were directly affected including 1221 deaths (mean case fatality ratio (CFR): 1.14% (95% confidence interval (CI) 1.07%-1.20%)). The highest CFR was observed for diseases targeted for eradication or elimination: 3.45% (95% CI 0.89%-10.45%). The African region remains prone to outbreaks of infectious diseases. It is therefore critical that Member States improve their capacities to rapidly detect, report and respond to public health events.

Use of a mobile application for Ebola contact tracing and monitoring in northern Sierra Leone: a proof-of-concept study

Background

The 2014–2016 Ebola epidemic in West Africa was the largest Ebola epidemic to date. Contact tracing was a core surveillance activity. Challenges with paper-based contact tracing systems include incomplete identification of contacts, delays in communication and response, loss of contact lists, inadequate data collection and transcription errors.

The aim of this study was to design and evaluate an electronic system for tracing contacts of Ebola cases in Port Loko District, Sierra Leone, and to compare this with the existing paper-based system. The electronic system featured data capture using a smartphone application, linked to an alert system to notify the District Ebola Response Centre of symptomatic contacts.

Methods

The intervention was a customised three-tier smartphone application developed using Dimagi’s CommCare platform known as the Ebola Contact Tracing application (ECT app). Eligible study participants were all 26 Contact Tracing Coordinators (CTCs) and 86 Contact Tracers (CTs) working in the 11 Chiefdoms of Port Loko District during the study period (April–August 2015). Case detection was from 13th April to 17th July 2015. The CTCs and their CTs were provided with smartphones installed with the ECT app which was used to conduct contact tracing activities. Completeness and timeliness of contact tracing using the app were compared with data from April 13th-June 7th 2015, when the standard paper-based system was used.

Results

For 25 laboratory-confirmed cases for whom paper-based contact tracing was conducted, data for only 39% of 408 contacts were returned to the District, and data were often incomplete. For 16 cases for whom app-based contact tracing was conducted, 63% of 556 contacts were recorded as having been visited on the app, and the median recorded duration from case confirmation to first contact visit was 70 h.

Conclusion

There were considerable challenges to conducting high-quality contact tracing in this setting using either the paper-based or the app-based system. However, the study demonstrated that it was possible to implement mobile health (mHealth) in this emergency setting. The app had the benefits of improved data completeness, storage and accuracy, but the challenges of using an app in this setting and epidemic context were substantial.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-4354-z) contains supplementary material, which is available to authorized users.

Clinical Surveillance and Evaluation of Suspected Ebola Cases in a Vaccine Trial During an Ebola Epidemic: The Sierra Leone Trial to Introduce a Vaccine Against Ebola

Clinical Trials Registration

ClinicalTrials.gov [NCT02378753] and Pan African Clinical Trials Registry [PACTR201502001037220].

Field-based evaluation of malaria outbreak detection and response in Mudzi and Goromonzi districts, Zimbabwe - 2017

National-level evaluations may fail to identify capacity improvements for detecting and responding to outbreaks which begin and are first detected at the local level. In response to this issue, we conducted a field-based assessment of the malaria outbreak surveillance system in Mashonaland East, Zimbabwe. We visited eleven clinics in Mudzi and Goromonzi districts. Twenty-one interviews were conducted with key informants from the provincial (n = 2), district (n = 7), and clinic (n = 12) levels. Interviews focused on surveillance system activities, preparedness, data quality, timeliness, stability, and usefulness. Main themes were captured utilising standard qualitative data analysis techniques. While the surveillance system detects malaria outbreaks at all levels, we identified several gaps. Clinics experience barriers to timely and reliable reporting of outbreaks to the district level and staff cross-training. Stability of resources, including transportation (33% of informants, n = 7) and staff capacity (48% of informants, n = 10), presented barriers. Strengthening these surveillance barriers may improve staff readiness to detect malaria outbreaks, resulting in timelier outbreak response and a reduction in malaria outbreaks, cases, and deaths. By focusing at the local level, our assessment approach provides a framework for identifying and addressing gaps that may be overlooked when utilising tools that evaluate surveillance capacity at the national level.

Improving health information systems during an emergency: lessons and recommendations from an Ebola treatment centre in Sierra Leone

Background

The 2014–2016 West Africa Ebola epidemic highlighted the difficulty of collecting patient information during emergencies, especially in highly infectious environments. Health information systems (HISs) appropriate for such settings were lacking prior to this outbreak. Here we describe our development and implementation of paper and electronic HISs at the Sierra Leone Kerry Town Ebola treatment centre (ETC) from 2014 to 2015. We share our approach, experiences, and recommendations for future health emergencies.

Methods

We developed eight fact-finding questions about data-related needs, priorities, and restrictions at the ETC (“inputs”) to inform eight structural decisions (“outputs”) across six core HIS components. Semi-structured interviews about the “inputs” were then conducted with HIS stakeholders, chosen based on their teams’ involvement in ETC HIS-related activities. Their responses were used to formulate the “output” results to guide the HIS design. We implemented the HIS using an Agile approach, monitored system usage, and developed a structured questionnaire on user experiences and opinions.

Results

Some key “input” responses were: 1) data needs for priorities (patient care, mandatory reporting); 2) challenges around infection control, limited equipment, and staff clinical/language proficiencies; 3) patient/clinical flows; and 4) weak points from staff turnover, infection control, and changing protocols. Key outputs included: 1) determining essential data, 2) data tool design decisions (e.g. large font sizes, checkboxes/buttons), 3) data communication methods (e.g. radio, “collective memory”), 4) error reduction methods (e.g. check digits, pre-written wristbands), and 5) data storage options (e.g. encrypted files, accessible folders). Implementation involved building data collection tools (e.g. 13 forms), preparing the systems (e.g. supplies), training staff, and maintenance (e.g. removing old forms). Most patients had basic (100%, n = 456/456), drug (96.9%, n = 442/456), and additional clinical/epidemiological (98.9%, n = 451/456) data stored. The questionnaire responses highlighted the importance of usability and simplicity in the HIS.

Conclusions

HISs during emergencies are often ad-hoc and disjointed, but systematic design and implementation can lead to high-quality systems focused on efficiency and ease of use. Many of the processes used and lessons learned from our work are generalizable to other health emergencies. Improvements should be started now to have rapidly adaptable and deployable HISs ready for the next health emergency.

Electronic supplementary material

The online version of this article (10.1186/s12911-019-0817-9) contains supplementary material, which is available to authorized users.

The Ebola virus disease outbreak in Tonkolili district, Sierra Leone: a retrospective analysis of the Viral Haemorrhagic Fever surveillance system, July 2014-June 2015

In Sierra Leone, the Ebola virus disease (EVD) outbreak occurred with substantial differences between districts with someone even not affected. To monitor the epidemic, a community event-based surveillance system was set up, collecting data into the Viral Haemorrhagic Fever (VHF) database. We analysed the VHF database of Tonkolili district to describe the epidemiology of the EVD outbreak during July 2014-June 2015 (data availability). Multivariable analysis was used to identify risk factors for EVD, fatal EVD and barriers to healthcare access, by comparing EVD-positive vs. EVD-negative cases. Key-performance indicators for EVD response were also measured. Overall, 454 EVD-positive cases were reported. At multivariable analysis, the odds of EVD was higher among those reporting contacts with an EVD-positive/suspected case (odds ratio (OR) 2.47; 95% confidence interval (CI) 2.44-2.50; P < 0.01) and those attending funeral (OR 1.02; 95% CI 1.01-1.04; P < 0.01). EVD cases from Kunike chiefdom had a lower odds of death (OR 0.22; 95% CI 0.08-0.44; P < 0.01) and were also more likely to be hospitalised (OR 2.34; 95% CI 1.23-4.57; P < 0.05). Only 25.1% of alerts were generated within 1 day from symptom onset. EVD preparedness and response plans for Tonkolili should include social-mobilisation activities targeting Ebola/knowledge-attitudes-practice during funeral attendance, to avoid contact with suspected cases and to increase awareness on EVD symptoms, in order to reduce delays between symptom onset to alert generation and consequently improve the outbreak-response promptness.

Recovering from the Ebola crisis: 'Social Reconnection Groups' in a rural Liberian community

In 2014/2015, International Medical Corps (IMC) operated two Ebola Treatment Units (ETUs) in Liberia and three in Sierra Leone when the Ebola virus disease epidemic killed over 11,000 people across Liberia, Sierra Leone and Guinea. As Ebola cases declined in Liberia, IMC Psychosocial teams transitioned to working in communities highly affected by the epidemic. This article describes IMC's experience with developing and implementing a community-based mental health and psychosocial group intervention in a rural, severely affected Liberian town - Mawah - where 46 out of approximately 800 community members were infected, 39 of whom died. In this paper, we present how the group intervention, named 'Social Reconnection Groups', was developed and implemented. We then discuss intervention strengths, challenges, key lessons learnt and recommendations for how Social Reconnection Groups can be adapted for use in similar settings.

Integrated Disease Surveillance and Response (IDSR) in Malawi: Implementation gaps and challenges for timely alert

Objective

The recent 2014 Ebola Virus Disease (EVD) outbreaks rang the bell to call upon global efforts to assist resource-constrained countries to strengthen public health surveillance system for early response. Malawi adopted the Integrated Disease Surveillance and Response (IDSR) strategy to develop its national surveillance system since 2002 and revised its guideline to fulfill the International Health Regulation (IHR) requirements in 2014. This study aimed to understand the state of IDSR implementation and differences between guideline and practice for future disease surveillance system strengthening.

Methods

This was a mixed-method research study. Quantitative data were to analyze completeness and timeliness of surveillance system performance from national District Health Information System 2 (DHIS2) during October 2014 to September 2016. Qualitative data were collected through interviews with 29 frontline health service providers from the selected district and 7 key informants of the IDSR system implementation and administration at district and national levels.

Findings

The current IDSR system showed relatively good completeness (73.1%) but poor timeliness (40.2%) of total expected monthly reports nationwide and zero weekly reports during the study period. Major implementation gaps were lack of weekly report and trainings. The challenges of IDSR implementation revealed through qualitative data included case identification, compiling reports for timely submission and inadequate resources.

Conclusions

The differences between IDSR technical guideline and actual practice were huge. The developing information technology infrastructure in Malawi and emerging mobile health (mHealth) technology can be opportunities for the country to overcome these challenges and improve surveillance system to have better timeliness for the outbreaks and unusual events detection.

The Politics of Disease Epidemics: a Comparative Analysis of the SARS, Zika, and Ebola Outbreaks

Over the past few decades, disease outbreaks have become increasingly frequent and widespread. The epicenters of these outbreaks have differed, and could be linked to different economic contexts. Arguably, the responses to these outbreaks have been "political" and inherently burdensome to marginalized populations. Key lessons can be learned from exploring the narratives about the different epidemics in varying income settings. Based on a review of the published medical, social, and political literature, which was accessed using four electronic databases-PubMed, Sociological Abstracts, Scholars Portal, and Web of Science, the overall objective of this paper discuss scholars' narratives on the "politics" of Ebola in a low-income setting, Zika virus in a middle-income setting, and SARS in a high-income setting. Various themes of the politics of epidemics were prominent in the literature. The narratives demonstrated the influence of power in whose narratives and what narratives are presented in the literature. While marginalized populations were reported to have borne the brunt of all disease outbreaks in the different contexts, the prevalence of their narratives within the reviewed literature was limited. Regardless of income setting, there is a need to give voice to the most marginalized communities during an epidemic. The experiences and narratives of those most vulnerable to an epidemic-specifically poor communities-need to be represented in the literature. This could contribute to mitigating some of the negative impact of the politics in epidemics.

Assessment of National Public Health and Reference Laboratory, Accra, Ghana, within Framework of Global Health Security

The Second Year of Life project of the Global Health Security Agenda aims to improve immunization systems and strengthen measles and rubella surveillance, including building laboratory capacity. A new laboratory assessment tool was developed by the Centers for Disease Control and Prevention to assess the national laboratory in Ghana to improve molecular surveillance for measles and rubella. Results for the tool showed that the laboratory is well organized, has a good capacity for handling specimens, has a good biosafety system, and is proficient for diagnosis of measles and rubella by serologic analysis. However, there was little knowledge about molecular biology and virology activities (i.e., virus isolation on tissue culture was not available). Recommendations included training of technical personnel for molecular techniques and advocacy for funding for laboratory equipment, reagents, and supplies.

Contact tracing performance during the Ebola virus disease outbreak in Kenema district, Sierra Leone

Contact tracing in an Ebola virus disease (EVD) outbreak is the process of identifying individuals who may have been exposed to infected persons with the virus, followed by monitoring for 21 days (the maximum incubation period) from the date of the most recent exposure. The goal is to achieve early detection and isolation of any new cases in order to prevent further transmission. We performed a retrospective data analysis of 261 probable and confirmed EVD cases in the national EVD database and 2525 contacts in the Contact Line Lists in Kenema district, Sierra Leone between 27 April and 4 September 2014 to assess the performance of contact tracing during the initial stage of the outbreak. The completion rate of the 21-day monitoring period was 89% among the 2525 contacts. However, only 44% of the EVD cases had contacts registered in the Contact Line List and 6% of probable or confirmed cases had previously been identified as contacts. Touching the body fluids of the case and having direct physical contact with the body of the case conferred a 9- and 20-fold increased risk of EVD status, respectively. Our findings indicate that incompleteness of contact tracing led to considerable unmonitored transmission in the early months of the epidemic. To improve the performance of early outbreak contact tracing in resource poor settings, our results suggest the need for prioritized contact tracing after careful risk assessment and better alignment of Contact Line Listing with case ascertainment and investigation.This article is part of the themed issue 'The 2013-2016 West African Ebola epidemic: data, decision-making and disease control'.

Analysis of patient data from laboratories during the Ebola virus disease outbreak in Liberia, April 2014 to March 2015

An outbreak of Ebola virus disease (EVD) in Liberia began in March 2014 and ended in January 2016. Epidemiological information on the EVD cases was collected and managed nationally; however, collection and management of the data were challenging at the time because surveillance and reporting systems malfunctioned during the outbreak. EVD diagnostic laboratories, however, were able to register basic demographic and clinical information of patients more systematically. Here we present data on 16,370 laboratory samples that were tested between April 4, 2014 and March 29, 2015. A total of 10,536 traceable individuals were identified, of whom 3,897 were confirmed cases (positive for Ebola virus RNA). There were significant differences in sex, age, and place of residence between confirmed and suspected cases that tested negative for Ebola virus RNA. Age (young children and the elderly) and place of residence (rural areas) were the risk factors for death due to the disease. The case fatality rate of confirmed cases decreased from 80% to 63% during the study period. These findings may help support future investigations and lead to a fuller understanding of the outbreak in Liberia.

Perspectives on model forecasts of the 2014-2015 Ebola epidemic in West Africa: lessons and the way forward

The unprecedented impact and modeling efforts associated with the 2014-2015 Ebola epidemic in West Africa provides a unique opportunity to document the performances and caveats of forecasting approaches used in near-real time for generating evidence and to guide policy. A number of international academic groups have developed and parameterized mathematical models of disease spread to forecast the trajectory of the outbreak. These modeling efforts often relied on limited epidemiological data to derive key transmission and severity parameters, which are needed to calibrate mechanistic models. Here, we provide a perspective on some of the challenges and lessons drawn from these efforts, focusing on (1) data availability and accuracy of early forecasts; (2) the ability of different models to capture the profile of early growth dynamics in local outbreaks and the importance of reactive behavior changes and case clustering; (3) challenges in forecasting the long-term epidemic impact very early in the outbreak; and (4) ways to move forward. We conclude that rapid availability of aggregated population-level data and detailed information on a subset of transmission chains is crucial to characterize transmission patterns, while ensemble-forecasting approaches could limit the uncertainty of any individual model. We believe that coordinated forecasting efforts, combined with rapid dissemination of disease predictions and underlying epidemiological data in shared online platforms, will be critical in optimizing the response to current and future infectious disease emergencies.

The health impact of the 2014-15 Ebola outbreak

OBJECTIVES

The 2014-15 outbreak in West Africa was the largest and deadliest Ebola outbreak recorded; however, there remains uncertainty over its wider health consequences. Our objective was to provide a comprehensive overview of the impact of the Ebola outbreak on population health in the three most affected countries: Sierra Leone, Liberia and Guinea.

STUDY DESIGN

Narrative review.

METHODS

A narrative overview of the peer-reviewed and grey literature related to the impact and consequences of the Ebola outbreak was conducted, synthesizing the findings of literature retrieved from a structured search of biomedical databases, the Web and references of reviewed articles.

RESULTS

The impact of the Ebola outbreak was profound and multifaceted. The health system was severely compromised due to overwhelming demand, healthcare workers deaths, resource diversion and closure of health facilities. Fear of Ebola and healthcare workers led to a breakdown in trust in health systems. Access to healthcare was compromised. Substantial reductions in healthcare utilization were reported including over 80% reductions in maternal delivery care in Ebola-affected areas, 40% national reductions in malaria admissions among children <5 years and substantial reductions in vaccination coverage. Socio-economic impacts included reduced community cohesion, education loss, reduced child protection, widespread job losses and food insecurity. Increased morbidity and mortality and reduced expected life expectancy were reported.

CONCLUSIONS

This review highlights the scope and scale of the consequences of the Ebola outbreak on population health. Sustained commitment of the international community is required to support health system re-building and to urgently address unmet population health needs.

Distinguishing epidemiological features of the 2013-2016 West Africa Ebola virus disease outbreak

The 2013-2016 West Africa Ebola virus disease epidemic was notable for its scope, scale, and complexity. This briefing presents a series of distinguishing epidemiological features that set this outbreak apart. Compared to one concurrent and 23 previous outbreaks of the disease over 40 years, this was the only occurrence of Ebola virus disease involving multiple nations and qualifying as a pandemic. Across multiple measures of magnitude, the 2013-2016 outbreak was accurately described using superlatives: largest and deadliest in terms of numbers of cases and fatalities; longest in duration; and most widely dispersed geographically, with outbreak-associated cases occurring in 10 nations. In contrast, the case-fatality rate was much lower for the 2013-2016 outbreak compared to the other 24 outbreaks. A population of particular interest for ongoing monitoring and public health surveillance is comprised of more than 17,000 "survivors," Ebola patients who successfully recovered from their illness. The daunting challenges posed by this outbreak were met by an intensive international public health response. The near-exponential rate of increase of incident Ebola cases during mid-2014 was successfully slowed, reversed, and finally halted through the application of multiple disease containment and intervention strategies.