What is Marburg Virus?
Marburg virus or simply Marburg is the common name for the the genus of viruses Marburgvirus, which contains one species, ''Lake Victoria marburgvirus''. The virus causes the disease Marburg Hemorrhagic Fever (MHF), also referred to as ''Marburg Virus Disease''. Marburg originated in Central and East Africa, and infects both human and nonhuman primates. The Marburg Virus is in the same taxonomic family as Ebola, and both are identical structurally although they elicit different antibodies.

The genera ''Marburgvirus'' and ''Ebolavirus'' were originally classified as the species of the now nonexistent ''Filovirus'' genus. In March 1998, the Vertebrate Virus Subcommittee proposed to the International Committee on Taxonomy of Viruses (ICTV) to change the ''Filovirus'' genus to ''Filovirus'' family with two specific genera: ''Ebola-like viruses'' and ''Marburg-like viruses''. This proposal was implemented in Washington DC as of April 2001 and in Paris as of July 2002. In 2000, another proposal was made in Washington DC to change the "-like viruses" to "-virus" (e.g. ''Ebolavirus'', ''Marburgvirus'') in addition to renaming the only species in the ''Marburgvirus'' genus from ''Marburg virus'' to ''Lake Victoria Marburgvirus''.

The item "Marburg" was named after the location of the first outbreak in 1967 in Marburg.

Marburg Virus Virology

Structure
The viral structure is typical of filoviruses, with long threadlike particles which have a consistent diameter but vary greatly in length from an average of 800 to 14,000 nanometers (nm), with peak infectious activity at about 790 nm. Virions (viral particles) contain seven known structural proteins. While nearly identical to Ebola virus in structure, Marburg virus is antigenically distinct from Ebola virus; in other words, it triggers different antibodies in infected organisms. It was the first filovirus to be identified.

Genome
Marburg contains a single molecule of linear negative-sense, 19100 nucleotides long, single-stranded RNA.

Natural reservoir
In September 2007, ''New Scientist'' magazine reported that the virus has been found in cave-dwelling African fruit bats in Gabon, the first time the virus has been found outside primates. The virus has now also been confirmed in bats in a Uganda mineafter two miners contracted Marburg in August 2007. Ebola antibodies (a close relative to Marburg) were found in three species of fruit bats in 2005. Marburg antibodies have been found in healthy bats, suggesting that the bats had been previously infected. Although no one has yet found complete live viruses from a bat, the team suggest that "[I think we can be sure that these fruit bats are the reservoir of Marburg virus".

The same techniques used to identify those genes were also used to identify Marburg genes found in Egyptian fruit bats, ''Rousettus aegyptiacus''.

Marburg Virus Epidemiology

Prevalence
Outbreaks of Marburg are centered in Africa, where the natural reservoir is believed to be located.

Transmission
The disease is spread through bodily fluids, including blood, excrement, saliva, and vomit. Early symptoms are often non-specific, and usually include fever, headache and myalgia after an incubation period of three to nine days. After five days, a maculopapular rash is often present on the trunk. Later-stage Marburg infection is acute and can include jaundice, pancreatitis, weight loss, delirium and neuropsychiatric symptoms, haemorrhaging, hypovolemic shock and multi-organ dysfunction, with liver failure most common. Accounts of external haemorrhaging from bodily orifices are pervasive in popular references to the disease but are in fact rare. Time course varies but symptoms usually last for one to three weeks until the disease either resolves or kills the infected host. The fatality rate is from 23% to over 90%.

Marburg Virus Medical aspects

Prevention
Caregivers require barrier infection control measures including double gloves, impermeable gowns, face shields, eye protection, leg and shoe coverings.

Marburg is a biosafety level-four agent, and thus requiring the highest level of precautions.

A few research groups are working on drugs and vaccines to fight the virus. In 1998, a group at the United States Army Medical Research Institute of Infectious Diseases (USAMRIID) published the first peer reviewed article detailing the development of the first experimental Marburg virus vaccine demonstrated to completely protect animals from lethal Marburg virus infection Following, in 2002, Genphar, a company doing research for the United States Army's biodefense program, announced that an experimental vaccine protected animals from a high dose of Marburg virus. The tests were conducted by the United States Army Medical Research Institute of Infectious Diseases (USAMRIID). According to the company, all animals in the control group died within days whereas all animals that received the regular dosage of the vaccine were fully protected.

In June 2005 scientists at Canada's National Microbiology Laboratory announced that they had also developed vaccines for both Marburg and Ebola that showed significant promise in primate testing. Studies on mice also suggested that the vaccine might be an effective treatment for the disease if it is administered shortly after a patient is infected. To make the vaccines the scientists fused a surface protein from the viruses they hope to protect against onto an animal virus - vesicular stomatitis - which is thought to be of no threat to humans. In the rhesus macaque monkey model of the disease, the vaccine is effective even when given after infection with the virus.

Symptoms
Many of the symptoms of Marburg haemorrhagic fever are similar to those of other infectious diseases, such as malaria or typhoid, but are most similar to those of Ebola strains.

Diagnosis
Diagnosis of Marburg is similar to Ebola using the Enzyme-Linked ImmunoSorbent Assay (ELISA) test.

Prognosis
If a patient survives, recovery is usually prompt and complete, though it may be prolonged in some cases, with inflammation or secondary infection of various organs, including: orchitis (testicles), hepatitis (liver), transverse myelitis (spinal cord), uveitis (eyes), and parotitis (salivary glands).

Treatment
There is no specific antiviral therapy indicated for treating Marburg, and hospital care is usually supportive in nature. Hypotension and shock may require early administration of vasopressors and haemodynamic monitoring with attention to fluid and electrolyte balance, circulatory volume, and blood pressure. Viral haemorrhagic fever (VHF) patients tend to respond poorly to fluid infusions and may develop pulmonary edema.


 

Research Team

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