The face of Ebola: changing frequency of haemorrhage in the West African compared with Eastern-Central African outbreaks

Enterotoxigenic Escherichia coli Heat-Stable Toxin and Ebola Virus Delta Peptide: Similarities and Differences

Enterotoxigenic Escherichia coli (ETEC) STb toxin exhibits striking structural similarity to Ebola virus (EBOV) delta peptide. Both ETEC and EBOV delta peptide are enterotoxins. Comparison of the structural and functional similarities and differences of these two toxins illuminates features that are important in induction of pathogenesis by a bacterial and viral pathogen.

Ebola virus delta peptide is an enterotoxin

During the 2013-2016 West African (WA) Ebola virus (EBOV) outbreak, severe gastrointestinal symptoms were common in patients and associated with poor outcome. Delta peptide is a conserved product of post-translational processing of the abundant EBOV soluble glycoprotein (sGP). The murine ligated ileal loop model was used to demonstrate that delta peptide is a potent enterotoxin. Dramatic intestinal fluid accumulation follows injection of biologically relevant amounts of delta peptide into ileal loops, along with gross alteration of villous architecture and loss of goblet cells. Transcriptomic analyses show that delta peptide triggers damage response and cell survival pathways and downregulates expression of transporters and exchangers. Induction of diarrhea by delta peptide occurs via cellular damage and regulation of genes that encode proteins involved in fluid secretion. While distinct differences exist between the ileal loop murine model and EBOV infection in humans, these results suggest that delta peptide may contribute to EBOV-induced gastrointestinal pathology.

Longitudinal in vivo imaging of acute neuropathology in a monkey model of Ebola virus infection

Ebola virus (EBOV) causes neurological symptoms yet its effects on the central nervous system (CNS) are not well-described. Here, we longitudinally assess the acute effects of EBOV on the brain, using quantitative MR-relaxometry, 18F-Fluorodeoxyglucose PET and immunohistochemistry in a monkey model. We report blood-brain barrier disruption, likely related to high cytokine levels and endothelial viral infection, with extravasation of fluid, Gadolinium-based contrast material and albumin into the extracellular space. Increased glucose metabolism is also present compared to the baseline, especially in the deep gray matter and brainstem. This regional hypermetabolism corresponds with mild neuroinflammation, sporadic neuronal infection and apoptosis, as well as increased GLUT3 expression, consistent with increased neuronal metabolic demands. Neuroimaging changes are associated with markers of disease progression including viral load and cytokine/chemokine levels. Our results provide insight into the pathophysiology of CNS involvement with EBOV and may help assess vaccine/treatment efficacy in real time.

Clinical and epidemiological performance of WHO Ebola case definitions: a systematic review and meta-analysis

BACKGROUND

Ebola virus disease case definition is a crucial surveillance tool to detect suspected cases for referral and as a screening tool for clinicians to support admission and laboratory testing decisions at Ebola health facilities. We aimed to assess the performance of the WHO Ebola virus disease case definitions and other screening scores.

METHODS

In this systematic review and meta-analysis, we searched PubMed, Scopus, Embase, and Web of Science for studies published in English between June 13, 1978, and Jan 14, 2020. We included studies that estimated the sensitivity and specificity of WHO Ebola virus disease case definitions, clinical and epidemiological characteristics (symptoms at admission and contact history), and predictive risk scores against the reference standard (laboratory-confirmed Ebola virus disease). Summary estimates of sensitivity and specificity were calculated using bivariate and hierarchical summary receiver operating characteristic (when four or more studies provided data) or random-effects meta-analysis (fewer than four studies provided data).

FINDINGS

We identified 2493 publications, of which 14 studies from four countries (Sierra Leone, Guinea, Liberia, and Angola) were included in the analysis. 12 021 people with suspected disease were included, of whom 4874 were confirmed as positive for Ebola virus infection. Six studies explored the performance of WHO case definitions in non-paediatric populations, and in all of these studies, suspected and probable cases were combined and could not be disaggregated for analysis. The pooled sensitivity of the WHO Ebola virus disease case definitions from these studies was 81·5% (95% CI 74·1-87·2) and pooled specificity was 35·7% (28·5-43·6). History of contact or epidemiological link was a key predictor for the WHO case definitions (seven studies) and for risk scores (six studies). The most sensitive symptom was intense fatigue (79·0% [95% CI 74·4-83·0]), assessed in seven studies, and the least sensitive symptom was pain behind the eyes (1·0% [0·0-7·0]), assessed in three studies. The performance of fever as a symptom varied depending on the cutoff used to define fever.

INTERPRETATION

WHO Ebola virus disease case definitions perform suboptimally to identify cases at both community level and during triage at Ebola health facilities. Inclusion of intense fatigue as a key symptom and contact history could improve the performance of case definitions, but implementation of these changes will require effective collaboration with, and trust of, affected communities.

FUNDING

Médecins sans Frontières.

Ebola virus: A global public health menace: A narrative review

Ebola virus disease (EVD), a fatal viral hemorrhagic illness, is due to infection with the Ebola virus of the Filoviridae family. The disease has evolved as a global public health menace due to a large immigrant population. Initially, the patients present with nonspecific influenza-like symptoms and eventually terminate into shock and multiorgan failure. There exists no specific treatment protocol for EVD and only supportive and symptomatic therapy is the line of treatment. This review article provides a detailed overview of the Ebola virus; it's clinical and oral manifestations, diagnostic aids, differential diagnosis, preventive aspects, and management protocol.

Experimental Infections of the Common Marmoset (Callithrix jacchus)

Interest in the use of marmosets for experimental infectious disease has dramatically increased in the last decade. These animals are native to the Atlantic coastal forests in northeastern Brazil. The majority of experimental animals come from the National Primate Research Centers and other breeding facilities. They are advantageous because of their relative small size, weighting 350–400 g as adults, their life span is compact compared with other nonhuman primate (NHP), and they produce offspring by 3 years of age. They are free of Herpes B virus and, it is believed, to date, other dangerous human pathogens (Abbot et al., 2003) [1]. We describe here the experimental infections of marmosets to human pathogens. While it is always interesting to compare various NHPs with each other, the importance of an animal model is always in comparing its similarities to human infections.

Predicting Ebola infection: A malaria-sensitive triage score for Ebola virus disease

Background

The non-specific symptoms of Ebola Virus Disease (EVD) pose a major problem to triage and isolation efforts at Ebola Treatment Centres (ETCs). Under the current triage protocol, half the patients allocated to high-risk “probable” wards were EVD(-): a misclassification speculated to predispose nosocomial EVD infection. A better understanding of the statistical relevance of individual triage symptoms is essential in resource-poor settings where rapid, laboratory-confirmed diagnostics are often unavailable.

Methods/Principal findings

This retrospective cohort study analyses the clinical characteristics of 566 patients admitted to the GOAL-Mathaska ETC in Sierra Leone. The diagnostic potential of each characteristic was assessed by multivariate analysis and incorporated into a statistically weighted predictive score, designed to detect EVD as well as discriminate malaria. Of the 566 patients, 28% were EVD(+) and 35% were malaria(+). Malaria was 2-fold more common in EVD(-) patients (p<0.05), and thus an important differential diagnosis. Univariate analyses comparing EVD(+) vs. EVD(-) and EVD(+)/malaria(-) vs. EVD(-)/malaria(+) cohorts revealed 7 characteristics with the highest odds for EVD infection, namely: reported sick-contact, conjunctivitis, diarrhoea, referral-time of 4–9 days, pyrexia, dysphagia and haemorrhage. Oppositely, myalgia was more predictive of EVD(-) or EVD(-)/malaria(+). Including these 8 characteristics in a triage score, we obtained an 89% ability to discriminate EVD(+) from either EVD(-) or EVD(-)/malaria(+).

Conclusions/Significance

This study proposes a highly predictive and easy-to-use triage tool, which stratifies the risk of EVD infection with 89% discriminative power for both EVD(-) and EVD(-)/malaria(+) differential diagnoses. Improved triage could preserve resources by identifying those in need of more specific differential diagnostics as well as bolster infection prevention/control measures by better compartmentalizing the risk of nosocomial infection.

Four decades after the discovery of Ebola virus disease (EVD), the sources, reservoirs and dynamics of infection are still largely unknown and thus the threat of re-emergence remains ever present. As EVD thrives on fragile healthcare systems in the developing world, it is essential that triage tools are low-cost and easy-to-use in order to best allocate limited resources and ensure sustainability of EVD surveillance. From a public health perspective, sensitivity is paramount when screening for highly contagious and fatal diseases such as Ebola. However, once these suspect patients arrive at the treatment centres, specificity becomes far more important in order to accurately allocate them to risk-appropriate wards and better distribute limited resources. Currently, pre-test triage to identify “suspect” Ebola patients consists of a binary evaluation of non-specific symptoms that are shared by the much more prevalent disease: Malaria. Using these guidelines, over 70% of patients selected for admission to the potentially contagious environment of an ETC did not have Ebola. Within the ETC, patients may be further triaged into a higher risk “probable” ward on the basis of a clinically subjective assessment known as the “Ebola look”: since proven to have comparable accuracy to flipping a coin. While compartmentalising risk by stratification is an essential component to infection prevention and control measures, patient triage should be sufficiently accurate to justify to its benefit. This study constructs an easy-to-use and highly accurate (90%) triage scoring system that discriminates EVD infection risk in a malaria-sensitive manner: a strategy, which not only significantly improves the predictive accuracy for EVD but may also identify the (more deadly) infection of malaria.

Ebola Virus Infection among Western Healthcare Workers Unable to Recall the Transmission Route

Introduction. During the 2014-2016 West-African Ebola virus disease (EVD) outbreak, some HCWs from Western countries became infected despite proper equipment and training on EVD infection prevention and control (IPC) standards. Despite their high awareness toward EVD, some of them could not recall the transmission routes. We explored these incidents by recalling the stories of infected Western HCWs who had no known directly exposures to blood/bodily fluids from EVD patients. Methodology. We carried out conventional and unconventional literature searches through the web using the keyword "Ebola" looking for interviews and reports released by the infected HCWs and/or the healthcare organizations. Results. We identified fourteen HCWs, some infected outside West Africa and some even classified at low EVD risk. None of them recalled accidents, unintentional exposures, or any IPC violation. Infection transmission was thus inexplicable through the acknowledged transmission routes. Conclusions. We formulated two hypotheses: inapparent exposures to blood/bodily fluids or transmission due to asymptomatic/mildly symptomatic carriers. This study is in no way intended to be critical with the healthcare organizations which, thanks to their interventions, put an end to a large EVD outbreak that threatened the regional and world populations.

Field Validation of the ReEBOV Antigen Rapid Test for Point-of-Care Diagnosis of Ebola Virus Infection

BACKGROUND

The 2013-2016 West African Ebola virus disease (EVD) epidemic is the largest recorded. Triage on the basis of clinical signs had limited success, and the time to diagnosis by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) could exceed 5 days. Here we describe the development and field validation of the ReEBOV Antigen Rapid Test (ReEBOV RDT) to aid triage of individuals with suspected EVD.

METHODS

Samples from patients with suspected EVD were submitted to Kenema Government Hospital, Sierra Leone, for Lassa fever and EVD screening throughout 2014. Banked residual clinical samples were tested in November 2014 and January 2015 in a blinded field trial to estimate the clinical effectiveness of the ReEBOV RDT, compared with EBOV-specific qRT-PCR.

RESULTS

Preliminary ReEBOV RDT performance demonstrated a positive percentage agreement (PPA) of 91.1% (195 of 214 results; 95% confidence interval [CI], 86.5%-94.6%) and a negative percentage agreement (NPA) of 90.2% (175 of 194; 95% CI, 85.1%-94.0%). The final estimates used by the Food and Drug Administration to determine whether to grant emergency use authorization for the test, which excluded a qRT-PCR reference method threshold cutoff, were a PPA of 62.1% (72 of 116 results; 95% CI, 52.6%-70.9%) and a NPA of 96.7% (58 of 60; 95% CI, 88.5%-99.6%), with a diagnostic likelihood of 18.6. A subsequent, independent evaluation by the World Health Organization generated results consistent with the preliminary performance estimates.

CONCLUSIONS

The ReEBOV RDT demonstrated the potential to provide clinically effective rapid and accurate point-of-care test results and, thus, to be a powerful tool for increasing triage efficiency.

An Outbreak of Ebola Virus Disease in the Lassa Fever Zone

BACKGROUND

Kenema Government Hospital (KGH) has developed an advanced clinical and laboratory research capacity to manage the threat of Lassa fever, a viral hemorrhagic fever (VHF). The 2013-2016 Ebola virus (EBOV) disease (EVD) outbreak is the first to have occurred in an area close to a facility with established clinical and laboratory capacity for study of VHFs.

METHODS

Because of its proximity to the epicenter of the EVD outbreak, which began in Guinea in March 2014, the KGH Lassa fever Team mobilized to establish EBOV surveillance and diagnostic capabilities.

RESULTS

Augustine Goba, director of the KGH Lassa laboratory, diagnosed the first documented case of EVD in Sierra Leone, on 25 May 2014. Thereafter, KGH received and cared for numbers of patients with EVD that quickly overwhelmed the capacity for safe management. Numerous healthcare workers contracted and lost their lives to EVD. The vast majority of subsequent EVD cases in West Africa can be traced back to a single transmission chain that includes this first diagnosed case.

CONCLUSIONS

Responding to the challenges of confronting 2 hemorrhagic fever viruses will require continued investments in the development of countermeasures (vaccines, therapeutic agents, and diagnostic assays), infrastructure, and human resources.