Marburg Marburgvirus: Infectious substances pathogen safety data sheet

Section I: Infectious agent

Name

Marburg Marburgvirus

Agent type

Virus

Taxonomy

Family

Filoviridae

Genus

Marburgvirus

Species

Marburg Marburgvirus

Subspecies/Strain/Clonal isolate

Marburg virus (MARV) and Ravn virus (RAVV)

Synonym or cross-reference

Common name Marburg virus (MARV). Also known as Marburg disease, Marburg virus disease (MVD), Marburg haemorrhagic fever and viral haemorrhagic fever^{Footnote 1}, ^{Footnote 2},^{Footnote 3},^{Footnote 4}. Formerly Lake Victoria Marburgvirus, Marburg virus haemorrhagic fever (MVHF).

Characteristics

Brief description

The genus Marburgvirus currently comprises a single species, Marburg marburgvirus, which is further subdivided into 2 distinct viruses, namely Marburg virus (MARV) and Ravn virus (RAVV)^{Footnote 4},^{Footnote 5}. The negative-sense, single-stranded enveloped RNA virus has variable morphology; virions are filamentous in shape but particles are pleomorphic and can be branched, circular, U-shaped or 6-shaped with spherical forms being rare to absent^{Footnote 1},^{Footnote 6}. Particle size is highly variable, with mean dimensions reporting an average length of 800 nm and average diameter of 80 nm^{Footnote 7}. Virions are composed of a central core, formed by a helical ribonucleoprotein (RNP) complex and surrounded by a matrix layer and a lipid envelope derived from host cell membranes^{Footnote 1}. Glycoprotein spikes are approximately 7 nm in diameter and are spaced at intervals of 10 nm on the surface of the virion. The Marburg virus genome is approximately 19.1 kb^{Footnote 8}.

Properties

In filoviruses, the viral life cycle first involves attachment of mature virus particles to the host cell via the viral glycoprotein (GP) binding to attachment factors^{Footnote 9}. The virus is then internalized primarily through micropinocytosis. In the endosome, GP is cleaved and binds to the endosomal receptor Niemann-Pick C1 (NPC1), initiating membrane fusion. Then, the viral nucleocapsid is released into the cytoplasm, where positive-sense transcripts and antigenomes are generated by the polymerase complex, and viral transcripts are translated by host ribosomes. Progeny virions are assembled and released via budding from the host cell. Peak infectivity has been associated with particles approximately 665 nm in length for marburgviruses^{Footnote 1}.

Section II: Hazard identification

Pathogenicity and toxicity

Severe acute illness, usually with sudden onset of fever^{Footnote 10}. MVD is typically broken down into 3 disease phases: initial generalization, early organ, and late organ/convalescent phases^{Footnote 10}. The initial generalization phase lasts for 5 days after disease onset and symptoms include: weakness, malaise, loss of appetite, limb pain, headache, fever, nausea, vomiting, diarrhea, and chills. Weight loss, abdominal, muscular and joint pain, as well as breathing difficulties are also common^{Footnote 11}. In 50–75% of patients, rapid debilitation, marked by gastrointestinal symptoms including anorexia, abdominal discomfort, severe nausea, vomiting, and diarrhea, occurs within 2–5 days^{Footnote 3}. The end of this initial phase is frequently characterized by conjunctivitis, dysphasia, enanthem, and pharyngitis^{Footnote 10}. A characteristic maculopapular rash may develop on body parts including the neck, back, and stomach. Other symptoms include lymphadenopathy, leukopenia, and thrombocytopenia^{Footnote 10},^{Footnote 12}. Early organ phase occurs during days 5 to 13, with illness progressing to neurological involvement, including confusion, encephalitis, irritability, delirium and aggression^{Footnote 3},^{Footnote 10}. Patients may also manifest conjunctival infection, prostration, shortness of breath, viral exanthema, irregular vascular permeability and edema. Approximately 75% of patients present with hemorrhagic manifestations, including mucosal bleeding, melena, petechiae, bloody diarrhea, visceral hemorrhagic effusions, hematemesis and ecchymosis. Subsequent death can occur within 1 to 2 weeks after symptom onset due to multiple organ failure^{Footnote 10}. Late Organ/ convalescent phase occurs between days 13 to 21 presenting as either a survivor or fatal case. Survivors enter a convalescence phase and may experience: myalgia, fibromyalgia, hepatitis, asthenia, ocular symptoms, and psychosis. Jaundice often accompanies terminal stages of illness along with coma, and convulsions^{Footnote 10},^{Footnote 13}. The case-fatality rate ranges from 25%-80% in reported cases with death occurring most often between days 8 to 16^{Footnote 2},^{Footnote 10}.

Marburg virus pathophysiology has been observed in animal models, including guinea pigs, mice, hamsters, baboons, and certain species of non-human primates, such as rhesus macaques, common marmosets, cynomolgus macaques, squirrel monkeys, and African green monkeys^{Footnote 10},^{Footnote 14}.

Epidemiology

Marburg virus infection in humans was first observed in Germany and Serbia in 1967 from laboratory acquired infections following handling of contaminated tissues obtained from African green monkeys imported from Uganda^{Footnote 10},^{Footnote 15}. This first reported outbreak affected 31 individuals, resulting in 7 deaths. Marburg virus infection is endemic in central and western Africa, including Zimbabwe, Kenya, Democratic Republic of Congo (DRC), Angola, and Uganda, and the disease is maintained in Egyptian fruit bats in endemic areas of Africa, which serve as a source of exposure for humans^{Footnote 16},^{Footnote 17}. Sporadic outbreaks in endemic areas as well as limited reporting of cases in individuals who had travelled to endemic areas have been reported. An outbreak occurred in Angola near the border of the DRC between October 2004 and August 2005, in which there were 329 deaths out of 374 reported cases representing a fatality rate of 88%^{Footnote 2}. Another outbreak occurred between 1998 and 2000 in the DRC with 128 deaths out of 154 cases representing a fatality rate of 83%. Between June 28 and September 16, 2022, Ghana reported the country's first outbreak of MVD, which involved 3 confirmed cases from the same household, including 2 deaths^{Footnote 18}. Infection is common among people living in urban or suburban areas^{Footnote 19},and healthcare workers^{Footnote 20}. Visits to bat-infested caves or mines^{Footnote 12}, and the improper handling of infected bodies^{Footnote 6} can also cause infections.

Pregnant women are more susceptible to filovirus (Marburg and Ebola) infection, with fetal loss rates approaching 100%^{Footnote 21}. Although pregnant women can recover, the fetus often dies due to transplacental or haematogenous spread of the virus^{Footnote 22}.

Behavioural and occupational factors, such as participating in funeral rites of a deceased MVD patient, providing care to an MVD patient, and visiting or working in caves or mines inhabited by bats are associated with an increased risk of infection and disease^{Footnote 23},^{Footnote 24},^{Footnote 25},^{Footnote 26},^{Footnote 27},^{Footnote 28}.

Host range

Natural host(s)

Bats, predominantly Egyptian Fruit bat (Rousettus aegyptiacus) are the primary hosts of Marburg virus^{Footnote 10}. Non-human primates and humans are secondary hosts.

Other host(s)

Guinea pigs, mice, hamsters, baboons, and certain species of non-human primates including rhesus macaques, common marmosets, cynomolgus macaques and African green monkeys^{Footnote 10},^{Footnote 29}.

Infectious dose

Although aerosol transmission of Marburg virus disease is not considered to be a primary mode of infection, viral hemorrhagic fevers have an experimentally determined infectious dose of 1 - 10 organisms by aerosol in non-human primates^{Footnote 30}. A lethal dose of 10 plaque forming units (pfu) administered intramuscularly in non-human primates has also been reported^{Footnote 31}. The median lethal dose was determined to be 0.015 50% tissue culture infective dose (TCID₅₀) of Marburg virus in severe combined immunodeficiency (SCID) mice^{Footnote 32}.

Incubation period

From 2 to 21 days; typically 5 to 9 days^{Footnote 10},^{Footnote 33},^{Footnote 38}.

Communicability

Blood, secretions, organs, or other excretions contain viable virus^{Footnote 2}. Human to human transmission or laboratory/nosocomial infection may occur following intimate contact with infected individuals, or tissue or excretions from infected individuals^{Footnote 34},^{Footnote 35}. Direct physical contact is typically required for the virus to spread^{Footnote 10}. Proper handling of the deceased is necessary to avoid viral transmission, as infection is still possible after death^{Footnote 2}. Transmission may also occur through contact with contaminated surfaces and fomites from sick patients^{Footnote 36}. Breast-feeding has been suggested as a plausible route of transmission based on epidemiological evidence wherein a high number of pediatric cases of infection were observed during an outbreak, and the virus was isolated from human breast milk^{Footnote 10},^{Footnote 37}.

Aerosol transmission has not been reported under natural conditions; however, evidence of aerosol transmission has been shown in experimental studies involving guinea pigs^{Footnote 38} and non-human primates^{Footnote 39},^{Footnote 40}. Macaques were exposed to aerosols of the Angola strain, while the guinea pigs were infected with the Popp strain. All animals died as a result of the exposure. In addition to virus being present in blood and soft tissues following exposure, guinea pigs were noted to shed virus in urine and faeces within 6 days of exposure to Marburg virus.

Apart from aerosol survival, MARV can also survive in liquids and on solid surfaces, including glasses and plastics, for more than 3 weeks at 4°C, indicating that fomite transmission of MARV can play an important role in spreading the virus^{Footnote 10},^{Footnote 41}. Other forms of MARV transmission include exposure of mucous membranes or breaks and abrasions in the skin, and the parenteral or enteral introduction of drugs and foods^{Footnote 10},^{Footnote 42}.

Section III: Dissemination

Reservoir

Bats, including the Egyptian Fruit Bat/Egyptian Flying Fox (Rousettus aegyptiacus), the Eloquent Horseshoe Bat (Rhinolophus eloquens) and Sundevall's roundleaf bat(Hipposideros caffer) are proposed reservoirs of infection^{Footnote 10},^{Footnote 43}. Viral DNA has been isolated infrequently in these bats at low levels^{Footnote 43}. Zoonotic transmission is supported by phylogenetic analysis indicating viral RNA fragments isolated from bats are similar to that isolated from clinical samples obtained from cases of human infection^{Footnote 44}. Antibodies specific for Marburg virus have also been detected in serum from Egyptian Fruit Bats^{Footnote 45}.

Zoonosis

Zoonotic transmission has been observed following exposure to bat habitats and following accidental exposure to infected monkey tissues^{Footnote 11},^{Footnote 38}. Zoonosis is suggested to occur from bat reservoir to humans through direct contact with infected bats or inhalation of aerosols of virus shed in bat urine, saliva, and feces^{Footnote 10}. Contact with monkeys or their bodily secretions can also lead to human infection^{Footnote 11}.

Vectors

Unknown. To date, arthropod vectors do not appear to contribute to the natural enzootic transmission of Marburg virus among Egyptian Fruit Bats (Rousettus aegyptiacus)^{Footnote 46}.

Section IV: Stability and viability

Drug susceptibility/resistance

Unknown. There is currently no treatment available for general use^{Footnote 10}. The treatment of Marburg virus disease is based solely on supportive care^{Footnote 38}.

Susceptibility to disinfectants

Marburg virus is inactivated by 1% sodium hypochlorite, 2% glutaraldehyde, formaldehyde, paraformaldehyde, formalin, 3% acetic acid, lipid solvents, and detergents^{Footnote 34}. Complete virus inactivation has been reported following chemical exposure (1:1 volume of diethyl ether in viral cell suspension at 4ᵒC for 1 hour; desoxycholate at 1:1000 volume in viral cell suspension at 37°C for 1 hour; 1% formalin for 1 hour at room temperature; 90% acetone at room temperature for 1 hour; 90% methyl alcohol at room temperature for 1 hour; and 1% Tego MGH at room temperature for 1 hour)^{Footnote 47},^{Footnote 48}. Blood diluted at 1:100 in 3% acetic acid for 15 minutes shows inactivation of Marburg virus^{Footnote 49}. Dilution of buffered tissue samples 1:1 in diethyl ether left to stand for 20 hours at 5°C have also been shown to completely inactivate the virus^{Footnote 50}. Dilution of infected tissue treated with β-propriolactone at a final concentration of 1:2000 for 24 hours at 4°C inactivated the virus^{Footnote 48}. Treatment of tissue dilutions with 0.5% phenol at room temperature for 1 hour reduced viable virus titers but did not completely inactivate the virus^{Footnote 48}.

Other methods have been suggested to inactivate Marburgvirus, but insufficient details are available to verify the efficacy of these methods. Lysis buffers such as 0.2% SDS, 0.1% Tween 20, buffers containing guanidine isothiocyanate with or without phenol^{Footnote 51},^{Footnote 52}; osmium tetroxide^{Footnote 50}; 1-3% N-chlorobenzensulfonamide; 1% sodium deoxycholate; sodium hypochlorite; acetone; and chloroform^{Footnote 52}.

Note: Decontamination requires specific, controlled use of virus-inactivating agents such as: trypsin, phenol, ether, formalin, or acetone^{Footnote 47}.

Physical inactivation

Complete virus inactivation has been reported following heat exposure (virus in cell suspension heated at 60°C for 60 minutes)^{Footnote 3},^{Footnote 12}, ultraviolet light exposure (cellular suspension in plastic wells exposed to a 30 Watt UV light for 2 minutes)^{Footnote 47}, and gamma radiation (1.27 x10⁶ rads at 4°C in sealed plastic tubes containing small volumes of virus in serum)^{Footnote 53}. Heat inactivation has also been reported at 56°C for 30 minutes^{Footnote 47}.

Survival outside host

Marburg virus remains stable in the environment after drying^{Footnote 54}. The virus is stable stored as tissue suspensions at -70°C for at least 1 year, and 4°C or room temperature for up to 5 weeks^{Footnote 30},^{Footnote 47}, with no reduction in infectivity observed^{Footnote 47}. Samples of virus diluted in culture media or guinea pig sera were stored at 4°C and room temperature with 50-60% humidity for up to 50 days. All samples contained virus at minimal detectable levels by day 46^{Footnote 30}.

Marburg virus may survive on contaminated surfaces for up to 46 days^{Footnote 30}. Virus diluted in either tissue culture media or guinea pig serum was allowed to dry on polyvinyl chloride, stainless steel, or glass. Samples were stored at either 4°C or room temperature and 50-60% humidity. Viable virus was not isolated from stainless steel, or any sample stored at room temperature at any time. Viable virus recovery on glass or plastic substrates reduced in a logarithmic pattern over the study period, with very little virus recovered at day 26 and no viable virus isolated at day 50^{Footnote 30}.

Aerosolized virus maintained at 19-25°C and 50-60% humidity showed logarithmic decay^{Footnote 29},^{Footnote 30}, with an estimated 14 minute half-life and 99% reduction in viability observed by 93 minutes post-aerosolization^{Footnote 30}.

Section V: First aid/medical

Surveillance

Monitor anyone suffering from an acute febrile illness that has recently travelled to rural sub-Saharan Africa, especially if haemorrhagic manifestations occur^{Footnote 55}. Diagnosis can be quickly done in an appropriately equipped laboratory using a multitude of approaches, including ELISA to detect anti-Marburg antibodies or viral antigens, RT-PCR to detect viral RNA, immunoelectron microscopy to detect virus particles in tissues and cells, and indirect immunofluorescence to detect antiviral antibodies^{Footnote 12},^{Footnote 32},^{Footnote 56},^{Footnote 57}. PCR is the quickest and most reliable detection method in emergency situations^{Footnote 11},^{Footnote 58}.

Note: The specific recommendations for surveillance in the laboratory should come from the medical surveillance program, which is based on a local risk assessment of the pathogens and activities being undertaken, as well as an overarching risk assessment of the biosafety program as a whole. More information on medical surveillance is available in the Canadian Biosafety Handbook (CBH).

First aid/treatment

Treatment of Marburg virus disease is currently supportive and directed at maintaining renal function and electrolyte balance, and combating haemorrhage and shock^{Footnote 32},^{Footnote 38}. Therapeutics such as antivirals (e.g., remdesivir, galidesivir, favipiravir) and MARV-specific monoclonal antibodies have been evaluated in non-human primates^{Footnote 59}.

Note: The specific recommendations for first aid/treatment in the laboratory should come from the post-exposure response plan, which is developed as part of the medical surveillance program. More information on the post-exposure response plan can be found in the CBH.

Immunization

No vaccine is currently available in Canada. However, candidate vaccines are in preclinical and clinical development. The MARV GP is the main antigen used in successful candidate vaccines.

The European Medicines Agency (EMA)-approved vaccine booster Mvabea^®(MVA-BN-Filo), a multivalent modified vaccinia ankara (MVA) encoding the GPs of Zaire ebolavirus (EBOV), Sudan ebolavirus (SUDV), Taï Forest ebolavirus (TAFV), and MARV, which is administered approximately 8-weeks post-vaccination with Zabdeno^®(Ad26 encoding EBOV-GP)^{Footnote 60}, may be explored for use as a booster vaccine in clinical trials for MVD vaccines^{Footnote 59}.

A multivalent adenovirus (Ad)-based vaccine is being developed by Janssen, Ad26.filo, which comprises 3 Ad26 vectors encoding the EBOV, SUDV, and MARV filovirus GPs^{Footnote 61}. A phase I, randomized, double-blind, placebo-controlled study assessed the safety, tolerability, and immunogenicity of heterologous regimens using the multivalent filovirus vaccines Ad26.filo and MVA-BN-Filo. Trial results showed the 2 dose regimens are well tolerated and immunogenic in healthy adults.

A replication-deficient recombinant chimpanzee adenovirus type 3 (cAd3)-vectored vaccine encoding a wild-type MARV Angola GP was evaluated in a phase 1, open-label, dose-escalation trial^{Footnote 62}. Trial results showed the candidate vaccine is safe and immunogenic. Future trials include a planned outbreak response clinical protocol (Ghana), a phase 2 clinical trial in Kenya and Uganda, and a phase 1b clinical trial in the USA.

Note: More information on the medical surveillance program can be found in the CBH, and by consulting the Canadian Immunization Guide.

Prophylaxis

There is no known post-exposure prophylaxis. However, post-exposure prophylactic vaccination against MARV has been evaluated in preclinical animal models^{Footnote 63}. The candidate vaccines are recombinant vesicular stomatitis virus-based vector encoding MARV GP (rVSVΔG-MARV-GP), which were evaluated in rhesus monkeys^{Footnote 63},^{Footnote 64},^{Footnote 65}.

Note: More information on prophylaxis as part of the medical surveillance program can be found in the CBH.

Section VI: Laboratory hazard

Laboratory-acquired infections

Several cases of laboratory-acquired infection were reported from laboratories in Germany and Serbia in 1967, with 25 reported primary cases of infection with 7 subsequent deaths^{Footnote 23}. The cases arose from accidental contact with blood and tissues from infected African green monkeys imported from Uganda^{Footnote 10}. Six secondary cases (medical personnel, 1 spouse) were developed from the primary cases. Three additional laboratory-acquired infections were reported in Russia in 1988, 1991 and 1995^{Footnote 38}.

Note: Please consult the Canadian Biosafety Standard (CBS) and CBH for additional details on requirements for reporting exposure incidents. A Canadian biosafety guideline describing notification and reporting procedures is also available.

Sources/specimens

Human sources/specimens reported to contain viable virus include blood, serum, urine, seminal fluid material collected from mucous membranes (throat, nose), and breast milk^{Footnote 10},^{Footnote 38}.

Animal sources/specimens reported to contain viable virus include blood, saliva, soft tissues, urine, and feces^{Footnote 10}.

Primary hazards

Accidental parenteral inoculation, respiratory exposure to experimentally infectious aerosols, and mucous membrane exposure to infectious droplets^{Footnote 66},^{Footnote 67}.

Special hazards

None.

Section VII: Exposure controls/personal protection

Risk group classification

Marburg marburgvirus is a Risk Group 4 (RG4) Human Pathogen and RG4 Animal Pathogen and a Security Sensitive Biological Agent (SSBA)^{Footnote 68}.

Containment requirements

Containment Level 4 facilities, equipment, and operational practices outlined in the CBS for work involving infectious or potentially infectious materials, animals, or cultures.

Note that there are additional security requirements, such as obtaining a Human Pathogens and Toxins Act Security Clearance, for work involving SSBAs.

Protective clothing

The applicable Containment Level 4 requirements for personal protective equipment and clothing outlined in the CBS to be followed. The use of a positive-pressure suit or use of a Class III biological safety cabinet (BSC) line is required for all work with RG4 pathogens.

Note: A local risk assessment will identify the appropriate hand, foot, head, body, eye/face, and respiratory protection, and the personal protective equipment requirements for the containment zone must be documented.

Other precautions

For Containment Level 4: All activities involving open vessels of regulated materials are to be performed in a certified biological safety cabinet (BSC) or other appropriate primary containment device. Centrifugation of infected materials must be carried out in closed containers placed in sealed safety cups, or in rotors that are unloaded in a biological safety cabinet. The integrity of positive pressure suits must be routinely checked for leaks. The use of needles, syringes, and other sharp objects is to be strictly limited. Open wounds, cuts, scratches, and grazes are to be covered with waterproof dressings. Additional precautions must be considered with work involving animal activities.

Section VIII: Handling and storage

Spills

The spill area is to be evacuated and secured. Aerosols must be allowed to settle for a minimum of 30 minutes. Spills of potentially contaminated material are to be covered with absorbent paper-based material (e.g., paper towels), liberally covered with an effective disinfectant (e.g., 1% sodium hypochlorite), and left to soak for an appropriate amount of time (e.g., 10 minutes) before being wiped up. Following the removal of the initial material, the disinfection process is to be repeated. Individuals performing this task must wear PPE, including particulate respirators (e.g., N95 or higher). Disposable gloves, impermeable gowns and protective eye wear are to be removed immediately after completion of the process, placed in an autoclave bag, and decontaminated prior to disposal (CBH).

Disposal

All materials/substances that have come in contact with the regulated materials must be completely decontaminated before they are removed from the containment zone. This can be achieved by using decontamination technologies and processes that have been demonstrated to be effective against the regulated materials, such as chemical disinfectants, autoclaving, irradiation, incineration, an effluent treatment system, or gaseous decontamination (CBH).

Storage

Containment Level 4: The applicable Containment Level 4 requirements for storage outlined in the CBS are to be followed. Pathogens, toxins, and other regulated materials to be stored inside the containment zone.
Inventory of Risk Group 4 (RG4) pathogens in long-term storage to be maintained and to include:

• specific identification of the pathogens, toxins, and other regulated materials; and
• a means to allow for the detection of a missing or stolen sample in a timely manner.

Section IX: Regulatory and other information

Canadian regulatory information

Controlled activities with Marburg marburgvirus require a Human Pathogens and Toxins Licence issued by the Public Health Agency of Canada. Marburg marburgvirus is a non-indigenous and emerging animal pathogen in Canada; therefore its importation requires an import permit, issued by the Canadian Food Inspection Agency.

Note that there are additional security requirements, such as obtaining a Human Pathogens and Toxins Act Security Clearance, for work involving SSBAs.

The following is a non-exhaustive list of applicable designations, regulations, or legislations:

• Human Pathogen and Toxins Act and Human Pathogens and Toxins Regulations
• Quarantine Act
• Transportation of Dangerous Goods Regulations
• Non-Indigenous Animal Pathogen or OIE-listed disease (please contact the Canadian Food Inspection Agency)

Last file update

February 2023

Prepared by

Centre for Biosecurity, Public Health Agency of Canada.

Disclaimer

The scientific information, opinions, and recommendations contained in this Pathogen Safety Data Sheet have been developed based on or compiled from trusted sources available at the time of publication. Newly discovered hazards are frequent and this information may not be completely up to date. The Government of Canada accepts no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information.

Persons in Canada are responsible for complying with the relevant laws, including regulations, guidelines and standards applicable to the import, transport, and use of pathogens in Canada set by relevant regulatory authorities, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment and Climate Change Canada, and Transport Canada. The risk classification and related regulatory requirements referenced in this Pathogen Safety Data Sheet, such as those found in the Canadian Biosafety Standard, may be incomplete and are specific to the Canadian context. Other jurisdictions will have their own requirements.

Copyright^© Public Health Agency of Canada, 2023, Canada