|Ebola virus under transmission electron microscope|
| Zaire ebolavirus |
The genus Ebolavirus ( // ee-BOH-lə-VY-rəs) is a virological taxon included in the family Filoviridae , order Mononegavirales . The members of this genus are called ebolaviruses. The six known virus species are named for the region where each was originally identified: Bundibugyo ebolavirus , Reston ebolavirus , Sudan ebolavirus , Taï Forest ebolavirus (originally Côte d'Ivoire ebolavirus), Zaire ebolavirus , and Bombali ebolavirus . The last is the most recent species to be named and was isolated from Angolan free-tailed bats in Sierra Leone.
Each species of the genus Ebolavirus has one member virus, and four of these cause Ebola virus disease (EVD) in humans, a type of hemorrhagic fever having a very high case fatality rate. The Reston virus has caused EVD in other primates.Zaire ebolavirus is the type species (reference or example species) for Ebolavirus, has the highest mortality rate of the ebolaviruses, and is responsible for the largest number of outbreaks of the six known species of the genus, including the 1976 Zaire outbreak and the outbreak with the most deaths (2014).
Ebolaviruses were first described after outbreaks of EVD in southern Sudan in June 1976 and in Zaire in August 1976.The name Ebolavirus is derived from the Ebola River in Zaire (now the Democratic Republic of the Congo), the location of the 1976 outbreak, and the taxonomic suffix -virus (denoting a viral genus). This genus was introduced in 1998 as the "Ebola-like viruses". In 2002, the name was changed to Ebolavirus and in 2010, the genus was emended. Ebolaviruses are closely related to marburgviruses.
Researchers have now found evidence of Ebola infection in three species of fruit bat. The bats show no symptoms of the disease, indicating that they may be the main natural reservoirs of the Ebolavirus. It is possible that there are other reservoirs and vectors. Understanding where the virus incubates between outbreaks and how it is transmitted between species will help protect humans and other primates from the virus.[ citation needed ]
The researchers found that bats of three species — Franquet's epauletted fruit bat ( Epomops franqueti ), the hammer-headed bat ( Hypsignathus monstrosus ) and the little collared fruit bat ( Myonycteris torquata ) — had either genetic material from the Ebola virus, known as RNA sequences, or evidence of an immune response to the disease. The bats showed no symptoms themselves.
The Bombali ebolavirus (BOMV) was isolated from the little free-tailed bat ( Chaerephon pumilus ) and the Angolan free-tailed bat ( Mops condylurus ) in Sierra Leone.
The entry pathway that the virus uses is a key step in its cycle. Several pathways have been suggested for Ebolavirus such as phagocytosis and clathrin and caveolin mediated endocytosis. However, Nanbo et al. (2010) proved that neither of these pathways is actually used.
They discovered that Ebolavirus uses macropinocytosis to enter the host cells. Induction of macropinocytosis leads to the formation of macropinocytosis-specific endosomes (macropinosomes), which are large enough to accommodate Ebola virions. This discovery was proven by the fact that Ebolavirus co-localizes with sorting nexin 5 (SNX5), which consists of a large family of peripheral membrane proteins that associate with newly formed macropinosomes.
Then, internalized EBOV particles are transported to late endosomes and, there, co-localization with GTPase Rab7 (marker of late endosomes) is observed.
Also, blocking the macropinocytosis pathway has been proven to stop Ebolavirus from entering the cells. Four different macropinocytosis specific inhibitors were tested: cytochalasin D (depolymerizing agent), wortmannin (Wort), LY-294002 (both are inhibitors of PI3K) and EIPA (5-(N-ethyl-N-isopropyl) amiloride), an inhibitor of the Na+/H+ exchanger specific for pinocytosis.
According to the rules for taxon naming established by the International Committee on Taxonomy of Viruses (ICTV), the name of the genus Ebolavirus is always to be capitalized, italicized, never abbreviated, and to be preceded by the word "genus". The names of its members (ebolaviruses) are to be written in lower case, are not italicized, and used without articles.
A virus of the family Filoviridae is a member of the genus Ebolavirus if
The genera Ebolavirus and Marburgvirus were originally classified as the species of the now-obsolete genus Filovirus. In March 1998, the Vertebrate Virus Subcommittee proposed in the International Committee on Taxonomy of Viruses (ICTV) to change the genus Filovirus to the family Filoviridae with two specific genera: Ebola-like viruses and Marburg-like viruses. This proposal was implemented in Washington, D.C., as of April 2001 and in Paris as of July 2002. In 2000, another proposal was made in Washington, D.C., to change the "-like viruses" to "-virus" resulting in today's Ebolavirus and Marburgvirus.
The five characterised species of the genus Ebolavirus are:
Rates of genetic change are 8*10−4 per site per year and are thus one fourthas fast as influenza A in humans. Extrapolating backwards, Ebolavirus and Marburgvirus probably diverged several thousand years ago. A study done in 1995 and 1996 found that the genes of Ebolavirus and Marburgvirus differed by about 55% at the nucleotide level, and at least 67% at the amino acid level. The same study found that the strains of Ebolavirus differed by about 37-41% across the nucleotide level and 34-43% across the amino acid level. The EBOV strain was found to have an almost 2% change in the nucleotide level from the original 1976 strain from the Yambuki outbreak and the strain from the 1995 Kikwit outbreak. However, paleoviruses of filoviruses found in mammals indicate that the family itself is at least tens of millions of years old.
The genus Ebolavirus has been organized into five species; however, the nomenclature has proven somewhat controversial, with many authors continuing to use common names rather than species names when referring to these viruses.In particular, the generic term "Ebola virus" is widely used to refer specifically to members of the species Zaire ebolavirus. Consequently, in 2010, a group of researchers recommended that the name "Ebola virus" be adopted for a subclassification within the species Zaire ebolavirus and that similar common names be formally adopted for other Ebolavirus species. In 2011, the International Committee on Taxonomy of Viruses (ICTV) rejected a proposal (2010.010bV) to formally recognize these names, as they do not designate names for subtypes, variants, strains, or other subspecies level groupings. As such, the widely used common names are not formally recognized as part of the taxonomic nomenclature. In particular, "Ebola virus" does not have an official meaning recognized by ICTV, and rather they continue to use and recommend only the species designation Zaire ebolavirus.
The threshold for putting isolates into different species is usually a difference of more than 30% at the nucleotide level, compared to the type strain. If a virus is in a given species but differs from the type strain by more than 10% at the nucleotide level, it is proposed that it be named as a new virus. As of 2019 [update] , none of the Ebolavirus species contain members divergent enough to receive more than one "virus" designation.
|Species name (Abbreviation)||Virus common name (Abbreviation)|
|Bombali ebolavirus||Bombali virus (BOMV)|
|Bundibugyo ebolavirus (BEBOV)||Bundibugyo virus (BDBV)|
|Reston ebolavirus (REBOV)||Reston virus (RESTV)|
|Sudan ebolavirus (SEBOV)||Sudan virus (SUDV)|
|Taï Forest ebolavirus (TEBOV; previously CIEBOV)||Taï Forest virus (TAFV)|
|Zaire ebolavirus (ZEBOV)||Ebola virus (EBOV)|
A 2013 study isolated antibodies from fruit bats in Bangladesh, against Ebola Zaire and Reston viruses, thus identifying potential virus hosts and signs of the filoviruses in Asia.
A recent alignment-free analysis of Ebola virus genomes from the current outbreak reveals the presence of three short DNA sequences that appear nowhere in the human genome, suggesting that the identification of specific species sequences may prove to be useful for the development of both diagnosis and therapeutics.
Marburg virus disease is a severe illness of humans and non-human primates caused by either of the two marburgviruses, Marburg virus (MARV) and Ravn virus (RAVV). MVD is a viral hemorrhagic fever (VHF), and the clinical symptoms are indistinguishable from Ebola virus disease (EVD).
The family Filoviridae, a member of the order Mononegavirales, is the taxonomic home of several related viruses that form filamentous infectious viral particles (virions) and encode their genome in the form of single-stranded negative-sense RNA. Two members of the family that are commonly known are Ebola virus and Marburg virus. Both viruses, and some of their lesser known relatives, cause severe disease in humans and nonhuman primates in the form of viral hemorrhagic fevers. All filoviruses are Select Agents, World Health Organization Risk Group 4 Pathogens, National Institutes of Health/National Institute of Allergy and Infectious Diseases Category A Priority Pathogens, Centers for Disease Control and Prevention Category A Bioterrorism Agents, and listed as Biological Agents for Export Control by the Australia Group.
The order Mononegavirales is the taxonomic home of numerous related viruses. Members of the order that are commonly known are, for instance, Ebola virus, human respiratory syncytial virus, measles virus, mumps virus, Nipah virus, and rabies virus. All of these viruses cause significant disease in humans. Many very important pathogens of nonhuman animals and plants are also members of this order.
The genus Marburgvirus is the taxonomic home of Marburg marburgvirus, whose members are the two known marburgviruses, Marburg virus (MARV) and Ravn virus (RAVV). Both viruses cause Marburg virus disease in humans and nonhuman primates, a form of viral hemorrhagic fever. Both are Select agents, World Health Organization Risk Group 4 Pathogens, National Institutes of Health/National Institute of Allergy and Infectious Diseases Category A Priority Pathogens, Centers for Disease Control and Prevention Category A Bioterrorism Agents, and are listed as Biological Agents for Export Control by the Australia Group.
Mayinga N'Seka was a nurse in Zaïre, now Democratic Republic of the Congo. She died from Ebola virus disease during the 1976 epidemic in Zaïre. She has been incorrectly identified as the index case by several sources, but a World Health Organization commission report on the outbreak lists a man from Yambuku, Mabalo Lokela, as the index case.
Cuevavirus is a genus in the family Filoviridae, which is included in the order Mononegavirales. Cuevavirus includes a single species, Lloviu cuevavirus, with one member, Lloviu virus (LLOV). It was discovered in the Cueva de Lloviu in Asturias, Spain, in a species of bats known as Schreiber's long-fingered bats. LLOV is a distant relative of the more widely known Ebola and Marburg viruses. Members of the genus are referred to as cuevaviruses. Cueva is derived from the Spanish word for cave.
The species Lloviu cuevavirus is the taxonomic home of a virus that forms filamentous virion, Lloviu virus (LLOV). The species is included in the genus Cuevavirus. LLOV is a distant relative of the commonly known Ebola virus and Marburg virus.
The species Bundibugyo ebolavirus is the taxonomic home of one virus, Bundibugyo virus (BDBV), that forms filamentous virions and is closely related to the infamous Ebola virus (EBOV). The virus causes severe disease in humans in the form of viral hemorrhagic fever and is a Select agent, World Health Organization Risk Group 4 Pathogen, National Institutes of Health/National Institute of Allergy and Infectious Diseases Category A Priority Pathogen, Centers for Disease Control and Prevention Category A Bioterrorism Agent, and is listed as a Biological Agent for Export Control by the Australia Group.
The species Taï Forest ebolavirus is a virological taxon included in the genus Ebolavirus, family Filoviridae, order Mononegavirales. The species has a single virus member, Taï Forest virus (TAFV). The members of the species are called Taï Forest ebolaviruses.
The species Sudan ebolavirus is a virological taxon included in the genus Ebolavirus, family Filoviridae, order Mononegavirales. The species has a single virus member, Sudan virus (SUDV). The members of the species are called Sudan ebolaviruses.
Reston virus (RESTV) is one of six known viruses within the genus Ebolavirus. Reston virus causes Ebola virus disease in non-human primates; unlike the other five ebolaviruses, it is not known to cause disease in humans, but has caused asymptomatic infections. Reston virus was first described in 1990 as a new "strain" of Ebola virus (EBOV). It is the single member of the species Reston ebolavirus, which is included into the genus Ebolavirus, family Filoviridae, order Mononegavirales. Reston virus is named after Reston, Virginia, US, where the virus was first discovered.
Marburg virus is a hemorrhagic fever virus of the Filoviridae family of viruses and a member of the species Marburg marburgvirus, genus Marburgvirus. Marburg virus (MARV) causes Marburg virus disease in humans and nonhuman primates, a form of viral hemorrhagic fever. The virus is considered to be extremely dangerous. The World Health Organization (WHO) rates it as a Risk Group 4 Pathogen. In the United States, the NIH/National Institute of Allergy and Infectious Diseases ranks it as a Category A Priority Pathogen and the Centers for Disease Control and Prevention lists it as a Category A Bioterrorism Agent. It is also listed as a biological agent for export control by the Australia Group.
Ravn virus is a close relative of the much more commonly known Marburg virus (MARV). RAVV causes Marburg virus disease in humans and nonhuman primates, a form of viral hemorrhagic fever. RAVV is a Select agent, World Health Organization Risk Group 4 Pathogen, National Institutes of Health/National Institute of Allergy and Infectious Diseases Category A Priority Pathogen, Centers for Disease Control and Prevention Category A Bioterrorism Agent, and listed as a Biological Agent for Export Control by the Australia Group.
Ebola virus disease (EVD), also known as Ebola haemorrhagic fever (EHF) or simply Ebola, is a viral haemorrhagic fever of humans and other primates caused by ebolaviruses. Signs and symptoms typically start between two days and three weeks after contracting the virus with a fever, sore throat, muscular pain, and headaches. Vomiting, diarrhoea and rash usually follow, along with decreased function of the liver and kidneys. At this time, some people begin to bleed both internally and externally. The disease has a high risk of death, killing 25% to 90% of those infected, with an average of about 50%. This is often due to low blood pressure from fluid loss, and typically follows 6 to 16 days after symptoms appear.
Zaire ebolavirus, more commonly known as Ebola virus, is one of six known species within the genus Ebolavirus. Four of the six known ebolaviruses, including EBOV, cause a severe and often fatal hemorrhagic fever in humans and other mammals, known as Ebola virus disease (EVD). Ebola virus has caused the majority of human deaths from EVD, and was the cause of the 2013–2016 epidemic in western Africa, which resulted in at least 28,646 suspected cases and 11,323 confirmed deaths.
In 2014, an outbreak of Ebola virus disease in the Democratic Republic of the Congo (DRC) occurred. Genome sequencing has shown that this outbreak was not related to the 2014–15 West Africa Ebola virus epidemic, but was of the same EBOV species. It began in August 2014 and was declared over in November of that year, after 42 days without any new cases. This is the 7th outbreak there, three of which occurred during the period of Zaire.
The Democratic Republic of the Congo (DRC) was identified by the World Health Organization (WHO) on 11 May 2017 as having one Ebola-related death.
Bombali ebolavirus or Bombali virus is a proposed species of Ebolavirus, first reported on 27 July 2018. It was discovered and sequenced by a research team from the U.S. in the Bombali area in the north of Sierra Leone, west Africa. The virus was found in the Angolan free-tailed bat and the Little free-tailed bat. In 2019, the virus was demonstrated in Angolan free-tailed bats in southeast Kenya and southeast Guinea. Bombali ebolavirus has the capacity to infect human cells, although it has not yet been shown to be pathogenic.
Mengla virus is a type of filovirus identified in a Rousettus bat in Mengla County, Yunnan Province, China and first reported in January 2019. It is classified in the same family as Ebolavirus and Marburgvirus.
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