Marburgvirus

Classification

Viruses; ssRNA viruses; ssRNA negative-strand viruses; Mononegavirales; Filoviridae

Species

Marburgvirus Marburg

Description and Significance

Marburg is an extremely dangerous virus as it has a human fatality rate of 25%, with outbreaks are impossible to predict or prevent.[1] Marburgvirus was the first ever filovirus recognized, discovered in 1967 when laboratory workers in Marburg, Germany developed hemorrhagic fever after handling tissue of African green monkeys from Uganda. The 1967 outbreak proved fatal in seven of the 37 cases. In 1975 the virus reemerged in Johannesburg, South Africa in a person who had been traveling in Zimbabwe. A traveling companion and a nurse of the person became infected. In 1980, another man who had been traveling near the same region became infected and transmitted the virus to his physician. Another Marburg infection was recognized in 1987 of a traveling man who became ill and soon died. In 1998, an outbreak occurred in Congo amongst individuals who had been working in a gold mine. Attempts to isolate the virus from all locations were unsuccessful. Since then, cases of Marburgvirus have been rare and sporadic, the most recent occurring in 2008 in Colorado of a man who had been traveling in Uganda.[5] The only other filovirus is the Ebola virus, discovered after Marburg in 1976.[3] The natural origins remain a complete mystery.[1]

Genome Structure

Negative stain image of an isolate of Marburg virus, 1000x magnification. Note filamentous particles [4].

Filoviruses are enveloped, nonsegmented negative-stranded RNA viruses. The two species, Marburg and Ebola virus, are genetically distinct with 7 genes and a total molecular length of approximately 19 kb (19112 bp), making them the owners of the largest known genomes of negative-strand RNA viruses. The virions appear long and filamentous, occasionally branched. In addition, the virions may appear as "6"-shaped, "U"-shaped, or circular configurations. [1][2]

Cell Structure, Metabolism and Life Cycle

Viruses are inherently dependent on a hosts machinery to replicate their genetic information. The viral genome encodes structural proteins and non-structural proteins. Virions consist of 5 structural proteins located in the envelope (surface glycoprotein), nucleocapsid (NP), polymerase complex (transcriptase-polymerase component and RNA-dependent RNA transcriptase-polymerase), matrix.[2]

Ecology and Pathogenesis

The natural history and origin of Marburg viruses remain a total mystery. It appears to be transmitted zoonotically; with human infection occuring from animals. However, all attempts to trace human cases have failed to uncover the reservoir. Speculations point to bats and rodents as probable reservoirs. Whatever the origin, human to human contact is the main route of infection and transmission in human filoviral hemorrhagic fever outbreaks. Marburg virus has been transmitted to primates by aerosol in laboratory experiments. [1] The disease is primarily spread through bodily fluids such as blood, excrement, saliva, and vomit. The hemorrhaging nature of Marburg infection is the main cause of prevalent transmission. Early symptoms are often mild fever and headache. 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 in many African cases has been as high as 90%.

References

[1] Beer et al., 1999: Beer Brigitte, Kurth Reinhard, Bukreyev Alexander Characteristics of Filoviridae: Marburg and Ebola viruses. Naturwissenschaften. 1999; 86(1): 8 - 17. [PubMed: 10024977].

[2] Marburg Virus Transmission [ http://staff.vbi.vt.edu/pathport/pathinfo/pathogens/Marburg_virus_2.html#Marburg_virus ] .

[3] Marburg Hemorrhagic Fever [ http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/marburg.htm ].

[4] Marburg Hemorrhagic Fever [ http://www.cdc.gov/ncidod/dvrd/spb/images/pix/pathimag/Marburg-emb.jpg ].

[5] CDC: Reported Marburg case [ http://www.medicalnewstoday.com/articles/138304.php ].

[6] ICTVdB Marburg: [ http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/01.025.0.01.htm#quickIDX2 ].