+ Genus<unk><unk> : species and its MVD-causing<unk> es Species name<unk>  name (Abbreviation)<unk> <unk><unk> *<unk><unk>  (MARV; previously MBGV) Ravn<unk>  (RAVV; previously MARV-Ravn) "*" denotes the type species. MVD is caused by two<unk> es;<unk><unk>  (MARV) and Ravn<unk>  (RAVV), family Filoviridae.<unk><unk> es are endemic in arid woodlands of equatorial Africa. Most<unk><unk>  infections were repeatedly associated with people visiting natural caves or working in mines. In 2009, the successful isolation of infectious MARV and RAVV was reported from healthy Egyptian rousette bats caught in caves. This isolation strongly suggests that Old World fruit bats are involved in the natural maintenance of<unk><unk> es and that visiting bat-infested caves is a risk factor for acquiring<unk><unk>  infections. Further studies are necessary to establish whether Egyptian rousettes are the actual hosts of MARV and RAVV or whether they get infected via contact with another animal and therefore serve only as intermediate hosts. Another risk factor is contact with nonhuman primates, although only one outbreak of MVD (in 1967) was due to contact with infected monkeys. Contrary to Ebola<unk><unk>  (EVD), which has been associated with heavy rains after long periods of dry weather, triggering factors for spillover of<unk><unk> es into the human population have not yet been described. Virology Genome Like all mononegaviruses,<unk> virions contain non-infectious, linear nonsegmented, single-stranded RNA genomes of negative polarity that possesses inverse-complementary 3' and 5' termini, do not possess a 5' cap, are not polyadenylated, and are not covalently linked to a protein.<unk><unk>  genomes are approximately 19 kb long and contain seven genes in the order 3'-UTR-NP-VP35-VP40-GP-VP30-VP24-L-5'-UTR. Structure Like all filoviruses,<unk> virions are filamentous particles that may appear in the shape of a shepherd's crook or in the shape of a "U" or a "6", and they may be coiled, toroid, or branched.<unk> virions are generally 80 nm in width, but vary somewhat in length. In general, the median particle length of<unk><unk> es ranges from 795–828 nm (in contrast to ebolavirions, whose median particle length was measured to be 974–1,086 nm ), but particles as long as 14,000 nm have been detected in tissue culture.<unk> virions consist of seven structural proteins. At the center is the helical ribonucleocapsid, which consists of the genomic RNA wrapped around a polymer of nucleoproteins (NP). Associated with the ribonucleoprotein is the RNA-dependent RNA polymerase (L) with the polymerase cofactor (VP35) and a transcription activator (VP30). The ribonucleoprotein is embedded in a matrix, formed by the major (VP40) and minor (VP24) matrix proteins. These particles are surrounded by a lipid membrane derived from the host cell membrane. The membrane anchors a glycoprotein (GP1,2) that projects 7 to 10 nm spikes away from its surface. Replication<unk><unk>  nucleocapsid The<unk><unk>  life cycle begins with virion attachment to specific cell-surface receptors, followed by fusion of the virion envelope with cellular membranes and the concomitant release of the<unk>  nucleocapsid into the cytosol. The<unk>  RdRp partially uncoats the nucleocapsid and transcribes the genes into positive-stranded mRNAs, which are then translated into structural and nonstructural proteins.<unk><unk>  L binds to a single promoter located at the 3' end of the genome. Transcription either terminates after a gene or continues to the next gene downstream. This means that genes close to the 3' end of the genome are transcribed in the greatest abundance, whereas those toward the 5' end are least likely to be transcribed. The gene order is therefore a simple but effective form of transcriptional regulation. The most abundant protein produced is the nucleoprotein, whose concentration in the cell determines when L switches from gene transcription to genome replication. Replication results in full-length, positive-stranded antigenomes that are in turn transcribed into negative-stranded<unk>  progeny genome copies. Newly synthesized structural proteins and genomes self-assemble and accumulate near the inside of the cell membrane. Virions bud off from the cell, gaining their envelopes from the cellular membrane they bud from. The mature progeny particles then infect other cells to repeat the cycle.
Marburg virus disease
Ebola
Pel–Ebstein fever
Crimean–Congo hemorrhagic fever
Barcoo fever
Mayaro virus disease
Typhoid fever
Dengue fever