Ebola virus disease contact tracing activities, lessons learned and best practices during the Duport Road outbreak in Monrovia, Liberia, November 2015

Targeted preventive vaccination campaigns to reduce Ebola outbreaks: An individual-based modeling study

INTRODUCTION

Nonpharmaceutical interventions (NPI) and ring vaccination (i.e., vaccination that primarily targets contacts and contacts of contacts of Ebola cases) are currently used to reduce the spread of Ebola during outbreaks. Because these measures are typically initiated after an outbreak is declared, they are limited by real-time implementation challenges. Preventive vaccination may provide a complementary option to help protect communities against unpredictable outbreaks. This study aimed to assess the impact of preventive vaccination strategies when implemented in conjunction with NPI and ring vaccination.

METHODS

A spatial-explicit, individual-based model (IBM) that accounts for heterogeneity of human contact, human movement, and timing of interventions was built to represent Ebola transmission in the Democratic Republic of the Congo. Simulated preventive vaccination strategies targeted healthcare workers (HCW), frontline workers (FW), and the general population (GP) with varying levels of coverage (lower coverage: 30% of HCW/FW, 5% of GP; higher coverage: 60% of HCW/FW, 10% of GP) and efficacy (lower efficacy: 60%; higher efficacy: 90%).

RESULTS

The IBM estimated that the addition of preventive vaccination for HCW reduced cases, hospitalizations, and deaths by ∼11 % to ∼25 % compared with NPI + ring vaccination alone. Including HCW and FW in the preventive vaccination campaign yielded ∼14 % to ∼38 % improvements in epidemic outcomes. Further including the GP yielded the greatest improvements, with ∼21 % to ∼52 % reductions in epidemic outcomes compared with NPI + ring vaccination alone. In a scenario without ring vaccination, preventive vaccination reduced cases, hospitalizations, and deaths by ∼28 % to ∼59 % compared with NPI alone. In all scenarios, preventive vaccination reduced Ebola transmission particularly during the initial phases of the epidemic, resulting in flatter epidemic curves.

CONCLUSIONS

The IBM showed that preventive vaccination may reduce Ebola cases, hospitalizations, and deaths, thus safeguarding the healthcare system and providing more time to implement additional interventions during an outbreak.

Coordinated support for local action: Modeling strategies to facilitate behavior adoption in urban-poor communities of Liberia for sustained COVID-19 suppression

BACKGROUND

Long-term suppression of SARS-CoV-2 transmission will involve strategies that recognize the heterogeneous capacity of communities to undertake public health recommendations. We highlight the epidemiological impact of barriers to adoption and the potential role of community-led coordination of support for cases and high-risk contacts in urban slums.

METHODS

A compartmental model representing transmission of SARS-CoV-2 in urban poor versus less socioeconomically vulnerable subpopulations was developed for Montserrado County, Liberia. Adoption of home-isolation behavior was assumed to be related to the proportion of each subpopulation residing in housing units with multiple rooms and with access to sanitation, water, and food. We evaluated the potential impact of increasing the maximum attainable proportion of adoption among urban poor following the scheduled lifting of the state of emergency.

RESULTS

Without intervention, the model estimated higher overall infection burden but fewer severe cases among urban poor versus the less socioeconomically vulnerable population. With self-isolation by mildly symptomatic individuals, median reductions in cumulative infections, severe cases, and maximum daily incidence were 7.6% (IQR: 2.2%-20.9%), 7.0% (2.0%-18.5%), and 9.9% (2.5%-31.4%), respectively, in the urban poor subpopulation and 16.8% (5.5%-29.3%), 15.0% (5.0%-26.4%), and 28.1% (9.3%-47.8%) in the less socioeconomically vulnerable population. An increase in the maximum attainable percentage of behavior adoption by the urban slum subpopulation was associated with median reductions of 19.2% (10.1%-34.0%), 21.1% (13.3%-34.2%), and 26.0% (11.5%-48.9%) relative to the status quo scenario.

CONCLUSIONS

Post-lockdown recommendations that prioritize home-isolation by confirmed cases are limited by resource constraints. Investing in community-based initiatives that coordinate support for self-identified cases and their contacts could more effectively suppress COVID-19 in settings with socioeconomic vulnerabilities.

A Mathematical Model of Contact Tracing during the 2014–2016 West African Ebola Outbreak

The 2014–2016 West African outbreak of Ebola Virus Disease (EVD) was the largest and most deadly to date. Contact tracing, following up those who may have been infected through contact with an infected individual to prevent secondary spread, plays a vital role in controlling such outbreaks. Our aim in this work was to mechanistically represent the contact tracing process to illustrate potential areas of improvement in managing contact tracing efforts. We also explored the role contact tracing played in eventually ending the outbreak. We present a system of ordinary differential equations to model contact tracing in Sierra Leonne during the outbreak. Using data on cumulative cases and deaths, we estimate most of the parameters in our model. We include the novel features of counting the total number of people being traced and tying this directly to the number of tracers doing this work. Our work highlights the importance of incorporating changing behavior into one’s model as needed when indicated by the data and reported trends. Our results show that a larger contact tracing program would have reduced the death toll of the outbreak. Counting the total number of people being traced and including changes in behavior in our model led to better understanding of disease management.

Ebola virus outbreak preparedness plan for developing Nations: Lessons learnt from affected countries

BACKGROUND

Ebola virus (EBOV); a public health emergency of international concern,is known to pose threat of global outbreaks. EBOV has spread in African continent and due to unchecked international travel, importation of cases has been reported in different countries. In this alarming scenario, developing countries need to evaluate and upgrade their preparedness plan to contain the spread of EBOV. The present review lays down the updated preparedness plan for developing countries to contain future EBOV outbreaks.

METHODS

The literature on EBOV outbreaks and preparedness strategies reported were searched on Pubmed and Google Scholar using the MeSH terms such as "Ebola virus disease, Epidemic, Outbreak, Imported case, Preparedness, Public health interventions" combined with Boolean operator (OR) for the period of 2011-2020. Additionally, World Health organization (WHO) and Centers for Disease Control & Prevention (CDC) websites were searched for the guidelines, reports, containment strategies, containment plan of countries, actions taken by countries and international partners, etc. RESULTS: The present review analyzed the EBOV outbreaks between 2011-2020 and containment strategies used by the affected countries. Based on the lessons learned from EBOV outbreaks and personal experience in infectious disease management, we have recommended a preparedness and response plan for EBOV containment in developing countries.

CONCLUSION

Developing countries are particularly vulnerable to major outbreaks of EBOV due to increased international travel and unchecked transmission. The recommended preparedness plan will help developing counties to contain EBOV outbreaks in future.

COVID-19 contact tracing: The Welsh experience

Objective

Contact tracing is one of the key public health response actions to control the outbreak of a novel virus. This paper describes the preparation process, activation and operational experience for contact tracing of individuals in response to confirmed COVID-19 cases in Wales.

Study design

A descriptive approach has been adopted and lessons learned from our initial public health response to COVID-19 will be used to develop a new operational model for contact tracing in Wales.

Methods

As part of preparations for the response in Wales, Public Health Wales formed a Contact Tracing Cell (CTC) ready to be mobilised in the event of a confirmed case.

Results

Trial activation of the CTC during the preparation period helped to resolve some issues before ‘real’ activation. A highly flexible approach was needed due to the constant changes to the guidance that required rapid understanding, updates to pathways and clear communication to contact tracers.

Conclusions

Our experience and recommendations may benefit future efforts to control the spread of the virus in Wales and elsewhere, particularly in supporting COVID-19 outbreaks in enclosed settings such as care homes or in geographically localised areas. Learning from the initial public health response to COVID-19 will guide the delivery and implementation of a new contact tracing model as we move to a later stage of the pandemic when containment measures become feasible in localised outbreaks. This may include scaling-up the CTC to mobilise contact tracers to local teams and the potential use of digital technologies to support the next operational model of the CTC in Wales.

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Contact tracing is one of the key public health response actions to control the outbreak of a novel virus.

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For a CTC to be effective, identification and training of adequate numbers of staff needs to be done as early as possible.

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A highly flexible approach was needed due to the logistical complexities of dealing with constant changes to the guidelines.

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The mobilisation of non-health protection staff freed up health protection teams to deal with more complex issues.

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Learning is needed to enhance future contact tracing activities when containment becomes feasible in localised outbreaks.

The practice of evaluating epidemic response in humanitarian and low-income settings: a systematic review

BACKGROUND

Epidemics of infectious disease occur frequently in low-income and humanitarian settings and pose a serious threat to populations. However, relatively little is known about responses to these epidemics. Robust evaluations can generate evidence on response efforts and inform future improvements. This systematic review aimed to (i) identify epidemics reported in low-income and crisis settings, (ii) determine the frequency with which evaluations of responses to these epidemics were conducted, (iii) describe the main typologies of evaluations undertaken and (iv) identify key gaps and strengths of recent evaluation practice.

METHODS

Reported epidemics were extracted from the following sources: World Health Organization Disease Outbreak News (WHO DON), UNICEF Cholera platform, Reliefweb, PROMED and Global Incidence Map. A systematic review for evaluation reports was conducted using the MEDLINE, EMBASE, Global Health, Web of Science, WPRIM, Reliefweb, PDQ Evidence and CINAHL Plus databases, complemented by grey literature searches using Google and Google Scholar. Evaluation records were quality-scored and linked to epidemics based on time and place. The time period for the review was 2010-2019.

RESULTS

A total of 429 epidemics were identified, primarily in sub-Saharan Africa, the Middle East and Central Asia. A total of 15,424 potential evaluations records were screened, 699 assessed for eligibility and 132 included for narrative synthesis. Only one tenth of epidemics had a corresponding response evaluation. Overall, there was wide variability in the quality, content as well as in the disease coverage of evaluation reports.

CONCLUSION

The current state of evaluations of responses to these epidemics reveals large gaps in coverage and quality and bears important implications for health equity and accountability to affected populations. The limited availability of epidemic response evaluations prevents improvements to future public health response. The diversity of emphasis and methods of available evaluations limits comparison across responses and time. In order to improve future response and save lives, there is a pressing need to develop a standardized and practical approach as well as governance arrangements to ensure the systematic conduct of epidemic response evaluations in low-income and crisis settings.

The implications of silent transmission for the control of COVID-19 outbreaks

Since the emergence of coronavirus disease 2019 (COVID-19), unprecedented movement restrictions and social distancing measures have been implemented worldwide. The socioeconomic repercussions have fueled calls to lift these measures. In the absence of population-wide restrictions, isolation of infected individuals is key to curtailing transmission. However, the effectiveness of symptom-based isolation in preventing a resurgence depends on the extent of presymptomatic and asymptomatic transmission. We evaluate the contribution of presymptomatic and asymptomatic transmission based on recent individual-level data regarding infectiousness prior to symptom onset and the asymptomatic proportion among all infections. We found that the majority of incidences may be attributable to silent transmission from a combination of the presymptomatic stage and asymptomatic infections. Consequently, even if all symptomatic cases are isolated, a vast outbreak may nonetheless unfold. We further quantified the effect of isolating silent infections in addition to symptomatic cases, finding that over one-third of silent infections must be isolated to suppress a future outbreak below 1% of the population. Our results indicate that symptom-based isolation must be supplemented by rapid contact tracing and testing that identifies asymptomatic and presymptomatic cases, in order to safely lift current restrictions and minimize the risk of resurgence.

Health system preparedness for emerging infectious diseases: A synthesis of the literature

This review reflects on what the literature to date has taught us about how health systems of low- and middle-income countries (LMICs) respond to emerging infectious disease (EID) outbreaks. These findings are then applied to propose a conceptual framework characterising an EID prepared health system. A narrative synthesis approach was adopted to explore the key elements of LMIC health systems during an EID outbreak. Overarching themes ('core health system constructs') and sub-themes ('elements') relevant to EID preparedness were extracted from 49 peer-reviewed articles. The resulting conceptual framework recognised six core constructs: four focused on material resources and structures (i.e. system 'hardware'), including (i) Surveillance, (ii) Infrastructure and medical supplies, (iii) Workforce, and (iv) Communication mechanisms; and two focused on human and institutional relationships, values and norms (i.e. system 'software'), including (i) Governance, and (ii) Trust. The article reinforces the interconnectedness of the traditional health system building blocks to EID detection, prevention and response, and highlights the critical role of system 'software' (i.e. governance and trust) in enabling LMIC health systems to achieve and maintain EID preparedness. The review provides recommendations for refining a set of indicators for an 'optimised' health system EID preparedness tool to aid health system strengthening efforts.

Persistence of Ebola virus after the end of widespread transmission in Liberia: an outbreak report

BACKGROUND

Outbreak response efforts for the 2014-15 Ebola virus disease epidemic in west Africa brought widespread transmission to an end. However, subsequent clusters of infection have occurred in the region. An Ebola virus disease cluster in Liberia in November, 2015, that was identified after a 15-year-old boy tested positive for Ebola virus infection in Monrovia, raised the possibility of transmission from a persistently infected individual.

METHODS

Case investigations were done to ascertain previous contact with cases of Ebola virus disease or infection with Ebola virus. Molecular investigations on blood samples explored a potential linkage between Ebola virus isolated from cases in this November, 2015, cluster and epidemiologically linked cases from the 2014-15 west African outbreak, according to the national case database.

FINDINGS

The cluster investigated was the family of the index case (mother, father, three siblings). Ebola virus genomes assembled from two cases in the November, 2015, cluster, and an epidemiologically linked Ebola virus disease case in July, 2014, were phylogenetically related within the LB5 sublineage that circulated in Liberia starting around August, 2014. Partial genomes from two additional individuals, one from each cluster, were also consistent with placement in the LB5 sublineage. Sequencing data indicate infection with a lineage of the virus from a former transmission chain in the country. Based on serology and epidemiological and genomic data, the most plausible scenario is that a female case in the November, 2015, cluster survived Ebola virus disease in 2014, had viral persistence or recurrent disease, and transmitted the virus to three family members a year later.

INTERPRETATION

Investigation of the source of infection for the November, 2015, cluster provides evidence of Ebola virus persistence and highlights the risk for outbreaks after interruption of active transmission. These findings underscore the need for focused prevention efforts among survivors and sustained capacity to rapidly detect and respond to new Ebola virus disease cases to prevent recurrence of a widespread outbreak.

FUNDING

US Centers for Disease Control and Prevention, Defense Threat Reduction Agency, and WHO.

Establishing Ebola Virus Disease (EVD) diagnostics using GeneXpert technology at a mobile laboratory in Liberia: Impact on outbreak response, case management and laboratory systems strengthening

The 2014-16 Ebola Virus Disease (EVD) outbreak in West Africa highlighted the necessity for readily available, accurate and rapid diagnostics. The magnitude of the outbreak and the re-emergence of clusters of EVD cases following the declaration of interrupted transmission in Liberia, reinforced the need for sustained diagnostics to support surveillance and emergency preparedness. We describe implementation of the Xpert Ebola Assay, a rapid molecular diagnostic test run on the GeneXpert platform, at a mobile laboratory in Liberia and the subsequent impact on EVD outbreak response, case management and laboratory system strengthening. During the period of operation, site coordination, management and operational capacity was supported through a successful collaboration between Ministry of Health (MoH), World Health Organization (WHO) and international partners. A team of Liberian laboratory technicians were trained to conduct EVD diagnostics and the laboratory had capacity to test 64-100 blood specimens per day. Establishment of the laboratory significantly increased the daily testing capacity for EVD in Liberia, from 180 to 250 specimens at a time when the effectiveness of the surveillance system was threatened by insufficient diagnostic capacity. During the 18 months of operation, the laboratory tested a total of 9,063 blood specimens, including 21 EVD positives from six confirmed cases during two outbreaks. Following clearance of the significant backlog of untested EVD specimens in November 2015, a new cluster of EVD cases was detected at the laboratory. Collaboration between surveillance and laboratory coordination teams during this and a later outbreak in March 2016, facilitated timely and targeted response interventions. Specimens taken from cases during both outbreaks were analysed at the laboratory with results informing clinical management of patients and discharge decisions. The GeneXpert platform is easy to use, has relatively low running costs and can be integrated into other national diagnostic algorithms. The technology has on average a 2-hour sample-to-result time and allows for single specimen testing to overcome potential delays of batching. This model of a mobile laboratory equipped with Xpert Ebola test, staffed by local laboratory technicians, could serve to strengthen outbreak preparedness and response for future outbreaks of EVD in Liberia and the region.