[Ebola and Marburg virus disease]. / Ebola-Virus- und Marburg-Viruserkrankung.

Viral hemorrhagic fevers (VHF) are serious, often fatal diseases that affect humans and non-human primates. The nomenclature of these diseases has changed in that they are now referred to as viral diseases because the previously named symptoms of fever or hemorrhages are not obligatory. In this article, the focus will be on the VHFs Ebola and Marburg viral disease with the potential for human-to-human transmission; these diseases are so-called high-consequence infectious diseases (HCID), some with considerable potential for epidemic spread and the risk of nosocomial transmission.

Reemergence of Marburgvirus disease: Update on current control and prevention measures and review of the literature.

In 1967, the very first case of the Marburgvirus disease (MVD) was detected in Germany and Serbia sequentially. Since then, MVD has been considered one of the most serious and deadly infectious diseases in the world with a case-fatality rate between 23% and 90% and a substantial number of recorded deaths. Marburgvirus belongs to the family of Filoviridae (filoviruses), which causes severe viral hemorrhagic fever (VHF). Some major risk factors for human infections are close contact with African fruit bats, MVD-infected non-human primates, and MVD-infected individuals. Currently, there is no vaccine or specific treatment for MVD, which emphasizes the seriousness of this disease. In July 2022, the World Health Organization reported outbreaks of MVD in Ghana after two suspected VHF cases were detected. This was followed in February and March 2023 with the emergence of the virus in two countries new to the virus: Equatorial Guinea and Tanzania, respectively. In this review, we aim to highlight the characteristics, etiology, epidemiology, and clinical symptoms of MVD, along with the current prevention measures and the possible treatments to control this virus.

Simultaneous detection of Marburg virus and Ebola virus with TaqMan-based multiplex real-time PCR method.

BACKGROUND: Marburg virus (MARV) and Ebola virus (EBOV) are acute infections with high case fatality rates. It is of great significance for epidemic monitoring and prevention and control of infectious diseases by the development of a rapid, specific, and sensitive quantitative PCR method to detect two pathogens simultaneously. METHODS: Primers and TaqMan probes were designed according to highly conserved sequences of these viruses. Sensitivity, specificity, linear range, limit of detection, and the effects of hemolysis and lipid on real-time qPCR were evaluated. RESULTS: The linearity of the curve allowed quantification of nucleic acid concentrations in range from 103 to 109  copies/ml per reaction (MARV and EBOV). The limit of detection of EBOV was 40 copies/ml, and MARV was 100 copies/ml. It has no cross-reaction with other pathogens such as hepatitis b virus (HBV), hepatitis c virus (HCV), human papillomavirus (HPV), Epstein-Barr virus (EBV), herpes simplex virus (HSV), cytomegalovirus (CMV), and human immunodeficiency virus (HIV). Repeatability analysis of the two viruses showed that their coefficient of variation (CV) was less than 5.0%. The above results indicated that fluorescence quantitative PCR could detect EBOV and MARV sensitively and specifically. CONCLUSIONS: The TaqMan probe-based multiplex fluorescence quantitative PCR assays could detect EBOV and MARV sensitively specifically and simultaneously.

Past and current advances in Marburg virus disease: a review.

Marburg Virus (MARV), along with the Ebola virus, belongs to the family of Filovirus and is cause of a lethal and severely affecting hemorrhagic fever. The Marburgvirus genus includes two viruses: MARV and Ravn. MARV has been recognized as one of utmost importance by the World Health Organization (WHO). The case fatality rate of the virus ranges from 24.0 to 88.0% which demonstrates its lethal nature and the need for its widespread information. The first case of the Marburgvirus disease (MARD) was reported in 1967 when lab personnel working with African green monkeys got infected in Germany and Serbia simultaneously. Following the initial case, many more outbreaks occurred around the world such as Uganda, Angola, Congo, Kenya and even in the United States in 2008. It was soon found out that the MARV was a zoonotic virus and mainly contracted from animal-to-human contact and further transmitted via human-to-human contact. The Egyptian fruit bat (Rousettus aegyptiacus) is known to be one of the significant sources of the infection and tourists visiting caves inhabited by these bats or workers accessing mines, populated by the bats, are at an increased risk of contracting the illness. The incubation period ranges from 2-21 days and the clinical outcome can be broken down into three phases: initial generalized phase (day 1-4), early organ phase (day 5 to 13) and either a late organ/convalescence phase (day 13 onwards). Furthermore, the treatment of MARD is solely based on supportive care. Much has been investigated in over the past half-century of the initial infection but only a few treatment options show promising results. In addition, special precaution is advised whilst handling the patient or the biospecimens. Disease-modifying agents and inhibitors of viral replications show constructive outcomes. It is crucial to identify the host of the virus and educate the populations that are greatly at risk of the disease. While much is being investigated to devise a vaccine, it is important to educate Health Care Workers (HCWs) and close contacts facing the illness. Stopping the transmission remains the best measure that can be taken.

A retrospective cohort investigation of seroprevalence of Marburg virus and ebolaviruses in two different ecological zones in Uganda.

BACKGROUND: Uganda has experienced seven Ebola Virus Disease (EVD) outbreaks and four Marburg Virus Disease (MVD) outbreaks between 2000 and 2019. We investigated the seroprevalence and risk factors for Marburg virus and ebolaviruses in gold mining communities around Kitaka gold mine in Western Uganda and compared them to non-mining communities in Central Uganda. METHODS: A questionnaire was administered and human blood samples were collected from three exposure groups in Western Uganda (gold miners, household members of miners, non-miners living within 50 km of Kitaka mine). The unexposed controls group sampled was community members in Central Uganda far away from any gold mining activity which we considered as low-risk for filovirus infection. ELISA serology was used to analyse samples, detecting IgG antibodies against Marburg virus and ebolaviruses (filoviruses). Data were analysed in STATA software using risk ratios and odds ratios. RESULTS: Miners in western Uganda were 5.4 times more likely to be filovirus seropositive compared to the control group in central Uganda (RR = 5.4; 95% CI 1.5-19.7) whereas people living in high-risk areas in Ibanda and Kamwenge districts were 3.6 more likely to be seropositive compared to control group in Luweeero district (RR = 3.6; 95% CI 1.1-12.2). Among all participants, filovirus seropositivity was 2.6% (19/724) of which 2.3% (17/724) were reactive to Sudan virus only and 0.1% (1/724) to Marburg virus. One individual seropositive for Sudan virus also had IgG antibodies reactive to Bundibugyo virus. The risk factors for filovirus seropositivity identified included mining (AOR = 3.4; 95% CI 1.3-8.5), male sex (AOR = 3.1; 95% CI 1.01-9.5), going inside mines (AOR = 3.1; 95% CI 1.2-8.2), cleaning corpses (AOR = 3.1; 95% CI 1.04-9.1) and contact with suspect filovirus cases (AOR = 3.9, 95% CI 1.04-14.5). CONCLUSIONS: These findings indicate that filovirus outbreaks may go undetected in Uganda and people involved in artisan gold mining are more likely to be exposed to infection with either Marburg virus or ebolaviruses, likely due to increased risk of exposure to bats. This calls for active surveillance in known high-risk areas for early detection and response to prevent filovirus epidemics.

Previremic Identification of Ebola or Marburg Virus Infection Using Integrated Host-Transcriptome and Viral Genome Detection.

Outbreaks of filoviruses, such as those caused by the Ebola (EBOV) and Marburg (MARV) virus, are difficult to detect and control. The initial clinical symptoms of these diseases are nonspecific and can mimic other endemic pathogens. This makes confident diagnosis based on clinical symptoms alone impossible. Molecular diagnostics for these diseases that rely on the detection of viral RNA in the blood are only effective after significant disease progression. As an approach to identify these infections earlier in the disease course, we tested the effectiveness of viral RNA detection combined with an assessment of sentinel host mRNAs that are upregulated following filovirus infection. RNAseq analysis of EBOV-infected nonhuman primates identified host RNAs that are upregulated at early stages of infection. NanoString probes that recognized these host-response RNAs were combined with probes that recognized viral RNA and were used to classify viral infection both prior to viremia and postviremia. This approach was highly successful at identifying samples from nonhuman primate subjects and correctly distinguished the causative agent in a previremic stage in 10 EBOV and 5 MARV samples. This work suggests that unified host response/viral fingerprint assays can enable diagnosis of disease earlier than testing for viral nucleic acid alone, which could decrease transmission events and increase therapeutic effectiveness.IMPORTANCE Current molecular tests that identify infection with high-consequence viruses such as Ebola virus and Marburg virus are based on the detection of virus material in the blood. These viruses do not undergo significant early replication in the blood and, instead, replicate in organs such as the liver and spleen. Thus, virus begins to accumulate in the blood only after significant replication has already occurred in those organs, making viremia an indicator of infection only after initial stages have become established. Here, we show that a multianalyte assay can correctly identify the infectious agent in nonhuman primates (NHPs) prior to viremia through tracking host infection response transcripts. This illustrates that a single-tube, sample-to-answer format assay could be used to advance the time at which the type of infection can be determined and thereby improve outcomes.

The Role of Reference Materials in the Research and Development of Diagnostic Tools and Treatments for Haemorrhagic Fever Viruses.

Following the Ebola outbreak in Western Africa in 2013-16, a global effort has taken place for preparedness for future outbreaks. As part of this response, the development of vaccines, treatments and diagnostic tools has been accelerated, especially towards pathogens listed as likely to cause an epidemic and for which there are no current treatments. Several of the priority pathogens identified by the World Health Organisation are haemorrhagic fever viruses. This review provides information on the role of reference materials as an enabling tool for the development and evaluation of assays, and ultimately vaccines and treatments. The types of standards available are described, along with how they can be applied for assay harmonisation through calibration as a relative potency to a common arbitrary unitage system (WHO International Unit). This assures that assay metrology is accurate and robust. We describe reference materials that have been or are being developed for haemorrhagic fever viruses and consider the issues surrounding their production, particularly that of biosafety where the viruses require specialised containment facilities. Finally, we advocate the use of reference materials at early stages, including research and development, as this helps produce reliable assays and can smooth the path to regulatory approval.

Marburgvirus in Egyptian Fruit Bats, Zambia.

We detected Marburg virus genome in Egyptian fruit bats (Rousettus aegyptiacus) captured in Zambia in September 2018. The virus was closely related phylogenetically to the viruses that previously caused Marburg outbreaks in the Democratic Republic of the Congo. This finding demonstrates that Zambia is at risk for Marburg virus disease.

Development, validation and clinical evaluation of a broad-range pan-filovirus RT-qPCR.

BACKGROUND: During the five decades since their discovery, filoviruses of four species have caused human hemorrhagic fever outbreaks: Marburg (MARV) marburgvirus, and Zaire (EBOV), Sudan (SUDV) and Bundybugyo (BDBV) ebolaviruses. The largest, devastating EBOV epidemic in West Africa in 2014-16, has been followed by outbreaks of MARV in Uganda, 2017, and EBOV in Democratic Republic of Congo, 2018, emphasizing the need to develop preparedness to diagnose all filoviruses. OBJECTIVES: The aim of this study was to optimize a new filovirus RT-qPCR to detect all filoviruses, define its limits of detection (LOD) and perform a field evaluation with outbreak samples. STUDY DESIGN: A pan-filovirus RT-qPCR targeting the L gene was developed and evaluated within the EbolaMoDRAD (Ebola virus: modern approaches for developing bedside rapid diagnostics) project. Specificity and sensitivity were determined and the effect of inactivation and PCR reagents (liquid and lyophilized format) were tested. RESULTS: The LODs for the lyophilized pan-filovirus L-RT-qPCR assay were 9.4 copies per PCR reaction for EBOV, 9.9 for MARV, 1151 for SUDV, 65 for BDBV and 289 for Taï Forest virus. The test was set at the Pasteur Institute, Dakar, Senegal, and 83 Ebola patient samples, with viral load ranging from 5 to 5 million copies of EBOV per reaction, were screened. The results for the patient samples were in 100% concordance with the reference EBOV-specific assay. DISCUSSION: Overall, the assay showed good sensitivity and specificity, covered all filoviruses known to be human pathogens, performed well both in lyophilized and liquid-phase formats and with EBOV outbreak clinical samples.

Marburg haemorrhagic fever in returning travellers: an overview aimed at clinicians.

Marburg virus haemorrhagic fever (MARV HF) is a dramatic disease that can occur in a traveller returning from an area where the virus is endemic. In this article, we provide an overview of MARV HF as an imported infection with an emphasis on clinical aspects. Although late features such as rash, signs of haemorrhagic diathesis and liver necrosis may point to the diagnosis, the initial clinical picture is non-specific. If in this early phase the patient's epidemiological exposure history is compatible with MARV HF, the patient should be isolated and managed according to viral haemorrhagic fever protocol and RT-PCR should be performed on the patient's blood as soon as possible to rule out MARV HF (or other possible viral haemorrhagic fevers). In severe cases, direct electron microscopy of blood in specialized centres (e.g. Bernhard-Nocht Institute in Hamburg, Germany) may be considered if the result of the RT-PCR is not readily available. Adequate diagnostics and empirical treatment for other acute life-threatening illnesses should not be withheld while test results are awaited, but all management and diagnostics should be weighed against the risks of nosocomial transmission.

Identity and validity of conserved B cell epitopes of filovirus glycoprotein: towards rapid diagnostic testing for Ebola and possibly Marburg virus disease.

BACKGROUND: Ebolavirus and Marburgvirus are genera of the virus family Filoviridae. Filoviruses cause rare but fatal viral hemorrhagic fevers (VHFs) in remote villages of equatorial Africa with potential for regional and international spread. Point-of-care (POC) rapid diagnostic tests (RDTs) are critical for early epidemic detection, reponse and control. There are 2 RDTs for Zaire ebolavirus (EBOV), but not other Ebolavirus spp. or Marburg marburgvirus (MARV). We validate 3 conserved B cell epitopes of filovirus glycoprotein (GP) using ebola virus diseases (EVD) survivor samples, towards devising pan-filovirus RDTs. METHODS: In-silico Immuno-informatics:- (a) multiple and basic local alignments of amino-acid sequences of filovirus (4 Ebolavirus spp. & MARV) Gp1, 2 and epitope prediction and conservation analyses within context of ClusterW, BLAST-P and the immune epitope database analysis resource (IEDB-AR); alongside (b) in-vitro enzyme immuno-assays (EIAs) for SUDV Gp1, 2 antigen and host-specific antibodies (IgM and IgG) among 94 gamma irradiated EVD survivor serum and 9 negative controls. RESULTS: Linear B cell epitopes were present across the entire length of all Gp1, 2, most lying in the region between amino acids positioned 350 and 500. Three seperate epitopes 97/80_GAFFLYDRLAST, 39_YEAGEWAENCY and 500_CGLRQLANETTQALQLFLRATTELR (designated UG-Filo-Peptide- 1, 2 and 3 respectively) were conserved within all studied filovirus species Gp1, 2. Gp1, 2 host specific IgM levels were comparably low (av. ODs < 0.04 [95% CI: 0.02837 to 0.04033]) among the 9 negative controls and 57 survivor samples analyzed. Host specific IgG levels, on the other hand, were elevated (av. ODs > 1.7525 [95% CI: 0.3010 to 3.1352]) among the 92 survivor samples relative to the 9 negative controls (av. ODs < 0.2.321 [95% CI: -0.7596 to 0.5372]). Filovirus Gp1, 2 antigen was not detected [av. ODs < 0.20] within EVD survivor serum relative to recombinant protein positive controls [av. ODs = 0.50]. CONCLUSIONS: These conserved B cell epitopes of filovirus Gp1, 2 and their derivative antibodies are promising for research and development of RDTs for EVD, with potential for extension to detect MVD.

How severe and prevalent are Ebola and Marburg viruses? A systematic review and meta-analysis of the case fatality rates and seroprevalence.

BACKGROUND: Ebola and Marburg virus diseases are said to occur at a low prevalence, but are very severe diseases with high lethalities. The fatality rates reported in different outbreaks ranged from 24-100%. In addition, sero-surveys conducted have shown different seropositivity for both Ebola and Marburg viruses. We aimed to use a meta-analysis approach to estimate the case fatality and seroprevalence rates of these filoviruses, providing vital information for epidemic response and preparedness in countries affected by these diseases. METHODS: Published literature was retrieved through a search of databases. Articles were included if they reported number of deaths, cases, and seropositivity. We further cross-referenced with ministries of health, WHO and CDC databases. The effect size was proportion represented by case fatality rate (CFR) and seroprevalence. Analysis was done using the metaprop command in STATA. RESULTS: The weighted average CFR of Ebola virus disease was estimated to be 65.0% [95% CI (54.0-76.0%), I2 = 97.98%] whereas that of Marburg virus disease was 53.8% (26.5-80.0%, I2 = 88.6%). The overall seroprevalence of Ebola virus was 8.0% (5.0%-11.0%, I2 = 98.7%), whereas that for Marburg virus was 1.2% (0.5-2.0%, I2 = 94.8%). The most severe species of ebolavirus was Zaire ebolavirus while Bundibugyo Ebolavirus was the least severe. CONCLUSIONS: The pooled CFR and seroprevalence for Ebola and Marburg viruses were found to be lower than usually reported, with species differences despite high heterogeneity between studies. Countries with an improved health surveillance and epidemic response have lower CFR, thereby indicating need for improving early detection and epidemic response in filovirus outbreaks.

Natural History of Aerosol Exposure with Marburg Virus in Rhesus Macaques.

Marburg virus causes severe and often lethal viral disease in humans, and there are currently no Food and Drug Administration (FDA) approved medical countermeasures. The sporadic occurrence of Marburg outbreaks does not allow for evaluation of countermeasures in humans, so therapeutic and vaccine candidates can only be approved through the FDA animal rule-a mechanism requiring well-characterized animal models in which efficacy would be evaluated. Here, we describe a natural history study where rhesus macaques were surgically implanted with telemetry devices and central venous catheters prior to aerosol exposure with Marburg-Angola virus, enabling continuous physiologic monitoring and blood sampling without anesthesia. After a three to four day incubation period, all animals developed fever, viremia, and lymphopenia before developing tachycardia, tachypnea, elevated liver enzymes, decreased liver function, azotemia, elevated D-dimer levels and elevated pro-inflammatory cytokines suggesting a systemic inflammatory response with organ failure. The final, terminal period began with the onset of sustained hypotension, dehydration progressed with signs of major organ hypoperfusion (hyperlactatemia, acute kidney injury, hypothermia), and ended with euthanasia or death. The most significant pathologic findings were marked infection of the respiratory lymphoid tissue with destruction of the tracheobronchial and mediastinal lymph nodes, and severe diffuse infection in the liver, and splenitis.

Ebola virus disease and Marburg disease in pregnancy: a review and management considerations for filovirus infection.

The largest-ever recorded outbreak of viral hemorrhagic fever is ongoing. As a result of the epidemic and rural nature of outbreaks, little is published about the Filovirus infections Ebola virus disease and Marburg disease in pregnancy. This review of viral hemorrhagic fever focusing on Marburg and Ebola uses knowledge of disease in nonpregnant individuals and pregnancy-specific data to inform management for pregnant women. Filovirus infection presentation is similar between pregnant and nonpregnant patients, although infections may be more severe in pregnancy. Although labeled as hemorrhagic fevers, Marburg and Ebola do not commonly cause gross bleeding and should be conceptualized as diseases of high gastrointestinal losses. Early, aggressive supportive care is the mainstay of Filovirus infection management with massive fluid resuscitation as the key management principle. Patients often require 5-10 L or more per day of intravenous or oral fluid to maintain circulating blood volume in the setting of ongoing gastrointestinal loss. Fluid shifts warrant aggressive monitoring and correction of potassium levels and acid-base disturbances to prevent life-threatening arrhythmias and metabolic complications. Regardless of maternal survival, fetal loss rates are nearly 100% in Filovirus infection, likely resulting from unchecked transplacental and hematogenous viral spread. High fetal loss rates support the placenta as a difficult-to-eradicate Filovirus infection reservoir. In conclusion, the management of Filovirus infection in pregnancy should focus on stabilizing the mother with intensive monitoring and aggressive fluid and electrolyte repletion as well as maintaining strict infection control to minimize transmission to others.

Ebola and Marburg haemorrhagic fever.

Ebolaviruses and Marburgviruses (family Filoviridae) are among the most virulent pathogens for humans and great apes causing severe haemorrhagic fever and death within a matter of days. This group of viruses is characterized by a linear, non-segmented, single-stranded RNA genome of negative polarity. The overall burden of filovirus infections is minimal and negligible compared to the devastation caused by malnutrition and other infectious diseases prevalent in Africa such as malaria, dengue or tuberculosis. In this paper, we review the knowledge gained on the eco/epidemiology, the pathogenesis and the disease control measures for Marburg and Ebola viruses developed over the last 15 years. The overall progress is promising given the little attention that these pathogen have achieved in the past; however, more is to come over the next decade given the more recent interest in these pathogens as potential public and animal health concerns. Licensing of therapeutic and prophylactic options may be achievable over the next 5-10 years.

Tissue and cellular tropism, pathology and pathogenesis of Ebola and Marburg viruses.

Ebola viruses and Marburg viruses include some of the most virulent and fatal pathogens known to humans. These viruses cause severe haemorrhagic fevers, with case fatality rates in the range 25-90%. The diagnosis of filovirus using formalin-fixed tissues from fatal cases poses a significant challenge. The most characteristic histopathological findings are seen in the liver; however, the findings overlap with many other viral and non-viral haemorrhagic diseases. The need to distinguish filovirus infections from other haemorrhagic fevers, particularly in areas with multiple endemic viral haemorrhagic agents, is of paramount importance. In this review we discuss the current state of knowledge of filovirus infections and their pathogenesis, including histopathological findings, epidemiology, modes of transmission and filovirus entry and spread within host organisms. The pathogenesis of filovirus infections is complex and involves activation of the mononuclear phagocytic system, with release of pro-inflammatory cytokines, chemokines and growth factors, endothelial dysfunction, alterations of the innate and adaptive immune systems, direct organ and endothelial damage from unrestricted viral replication late in infection, and coagulopathy. Although our understanding of the pathogenesis of filovirus infections has rapidly increased in the past few years, many questions remain unanswered.

Lyophilisation of influenza, rabies and Marburg lentiviral pseudotype viruses for the development and distribution of a neutralisation -assay-based diagnostic kit.

Pseudotype viruses (PVs) are chimeric, replication-deficient virions that mimic wild-type virus entry mechanisms and can be safely employed in neutralisation assays, bypassing the need for high biosafety requirements and performing comparably to established serological assays. However, PV supernatant necessitates -80°C long-term storage and cold-chain maintenance during transport, which limits the scope of dissemination and application throughout resource-limited laboratories. We therefore investigated the effects of lyophilisation on influenza, rabies and Marburg PV stability, with a view to developing a pseudotype virus neutralisation assay (PVNA) based kit suitable for affordable global distribution. Infectivity of each PV was calculated after lyophilisation and immediate reconstitution, as well as subsequent to incubation of freeze-dried pellets at varying temperatures, humidities and timepoints. Integrity of glycoprotein structure following treatment was also assessed by employing lyophilised PVs in downstream PVNAs. In the presence of 0.5M sucrose-PBS cryoprotectant, each freeze-dried pseudotype was stably stored for 4 weeks at up to 37°C and could be neutralised to the same potency as unlyophilised PVs when employed in PVNAs. These results confirm the viability of a freeze-dried PVNA-based kit, which could significantly facilitate low-cost serology for a wide portfolio of emerging infectious viruses.