Bunyaviridae
Encyclopedia
Bunyaviridae is a family of negative-stranded RNA virus
es. Though generally found in arthropod
s or rodents, certain viruses in this family occasionally infect humans. Some of them also infect plants.
Bunyaviridae are vector-borne viruses. With the exception of Hantaviruses, transmission occurs via an arthropod vector (mosquitos, tick, or sandfly). Hantaviruses are transmitted through contact with deer mice feces. Incidence of infection is closely linked to vector activity, for example, mosquito-borne viruses are more common in the summer.
Human infections with certain Bunyaviridae, such as Crimean-Congo hemorrhagic fever virus
, are associated with high levels of morbidity and mortality, consequently handling of these viruses must occur with a Biosafety level 4 laboratory. They are also the cause of severe fever with thrombocytopenia syndrome
.
Hanta virus or Hantavirus Hemorrhagic fever, common in Korea, Scandinavia, Russia, and western North American, is associated with high fever, lung edema and pulmonary failure. Mortality is around 55%.
The antibody reaction plays an important role in decreasing levels of viremia.
is somewhat similar to that of the Paramyxoviridae family; Bunyaviridae form enveloped, spherical virions with diameters of 90-100 nm. These viruses contain no matrix proteins.
s consisting of a large (L), medium (M), and small (S) RNA segment. These RNA segments are single-stranded, and exist in a helical formation within the virion. Besides, they exhibit a pseudo-circular structure due to each segment's complementary ends. The L segment encodes the RNA Dependent RNA-polymerase, necessary for viral RNA replication and mRNA synthesis. The M segment encodes the viral glycoprotein
s, which project from the viral surface and aid the virus in attaching to and entering the host cell. The S segment encodes the nucleocapsid protein (N).
The L and M segment are negative sense. For the Genera of Phlebovirus and Tospovirus, the S segment is ambisense. Ambisense means that some of the genes on the RNA strand are negative sense and others are positive sense. The S segment codes for the viral nucleoprotein (N) in the negative sense and a nonstructural
(NSs) protein in ambisense.
Total genome size ranges from 10.5 to 22.7 kbp.
Bunyavirus RNA replicates in the cytoplasm
, while the viral proteins transit through the ER
and Golgi apparatus
. Mature virions bud from the Golgi apparatus into vesicles which are transported to the cell surface.
and severe fever with thrombocytopenia syndrome
.
RNA virus
An RNA virus is a virus that has RNA as its genetic material. This nucleic acid is usually single-stranded RNA but may be double-stranded RNA...
es. Though generally found in arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
s or rodents, certain viruses in this family occasionally infect humans. Some of them also infect plants.
Bunyaviridae are vector-borne viruses. With the exception of Hantaviruses, transmission occurs via an arthropod vector (mosquitos, tick, or sandfly). Hantaviruses are transmitted through contact with deer mice feces. Incidence of infection is closely linked to vector activity, for example, mosquito-borne viruses are more common in the summer.
Human infections with certain Bunyaviridae, such as Crimean-Congo hemorrhagic fever virus
Crimean-Congo hemorrhagic fever
Crimean–Congo hemorrhagic fever is a widespread tick-borne viral disease, a zoonosis of domestic animals and wild animals, that may affect humans. The pathogenic virus, especially common in East and West Africa, is a member of the Bunyaviridae family of RNA viruses. Clinical disease is rare in...
, are associated with high levels of morbidity and mortality, consequently handling of these viruses must occur with a Biosafety level 4 laboratory. They are also the cause of severe fever with thrombocytopenia syndrome
Severe fever with thrombocytopenia syndrome
Severe fever with thrombocytopenia syndrome is an emerging infectious disease recently discovered in northeast and central China. SFTS cause high fatality rate of 12% and as high as 30% in some areas...
.
Hanta virus or Hantavirus Hemorrhagic fever, common in Korea, Scandinavia, Russia, and western North American, is associated with high fever, lung edema and pulmonary failure. Mortality is around 55%.
The antibody reaction plays an important role in decreasing levels of viremia.
Classification
The family Bunyaviridae contains the genera:- Genus HantavirusHantavirusHantaviruses are negative sense RNA viruses in the Bunyaviridae family. Humans may be infected with hantaviruses through rodent bites, urine, saliva or contact with rodent waste products...
; type species: Hantaan virus - Genus NairovirusNairovirusNairovirus is a genus in the family Bunyaviridae that include viruses with circular, negative-sense single stranded RNA. It got its name from the Nairobi sheep disease that affects the gastrointestinal tracts of sheep and goats...
; type species: Dugbe virus - Genus OrthobunyavirusOrthobunyavirusOrthobunyavirus is a genus of the Bunyaviridae family.The genus is most diverse in Africa, Australia and Oceania, but occurs almost world-wide...
; type species: Bunyamwera virus - Genus Phlebovirus; type species: Rift Valley fever virus
- Genus TospovirusTospovirusThe Tospoviruses are a genus of negative RNA virus found within the family Bunyaviridae. They are the sole group of plant infecting viruses in this family, as all other described members of the Bunyaviridae infect animals. The genus takes its name from the discovery of Tomato spotted wilt virus ...
; type species: Tomato spotted wilt virus
Structure
Bunyavirus morphologyMorphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
is somewhat similar to that of the Paramyxoviridae family; Bunyaviridae form enveloped, spherical virions with diameters of 90-100 nm. These viruses contain no matrix proteins.
Genome
Bunyaviridae have tripartite genomeGenome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
s consisting of a large (L), medium (M), and small (S) RNA segment. These RNA segments are single-stranded, and exist in a helical formation within the virion. Besides, they exhibit a pseudo-circular structure due to each segment's complementary ends. The L segment encodes the RNA Dependent RNA-polymerase, necessary for viral RNA replication and mRNA synthesis. The M segment encodes the viral glycoprotein
Glycoprotein
Glycoproteins are proteins that contain oligosaccharide chains covalently attached to polypeptide side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. In proteins that have segments extending...
s, which project from the viral surface and aid the virus in attaching to and entering the host cell. The S segment encodes the nucleocapsid protein (N).
The L and M segment are negative sense. For the Genera of Phlebovirus and Tospovirus, the S segment is ambisense. Ambisense means that some of the genes on the RNA strand are negative sense and others are positive sense. The S segment codes for the viral nucleoprotein (N) in the negative sense and a nonstructural
Nonstructural protein
In virology, a nonstructural protein is a protein encoded by a virus but it is not part of the viral particle....
(NSs) protein in ambisense.
Total genome size ranges from 10.5 to 22.7 kbp.
Replication
This ambisense arrangement requires two rounds of transcription to be carried out. First the negative sense RNA is transcribed to produce mRNA and a full length replicative intermediate. From this intermediate a subgenomic mRNA encoding the small segment nonstructural protein is produced while the polymerase produced following the first round of transcription can now replicate the full length of RNA to produce viral genomes.Bunyavirus RNA replicates in the cytoplasm
Cytoplasm
The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
, while the viral proteins transit through the ER
Endoplasmic reticulum
The endoplasmic reticulum is an organelle of cells in eukaryotic organisms that forms an interconnected network of tubules, vesicles, and cisternae...
and Golgi apparatus
Golgi apparatus
The Golgi apparatus is an organelle found in most eukaryotic cells. It was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named....
. Mature virions bud from the Golgi apparatus into vesicles which are transported to the cell surface.
Diseases
Infections with certain Bunyaviridae, cause a number of diseases including: Crimean-Congo hemorrhagic feverCrimean-Congo hemorrhagic fever
Crimean–Congo hemorrhagic fever is a widespread tick-borne viral disease, a zoonosis of domestic animals and wild animals, that may affect humans. The pathogenic virus, especially common in East and West Africa, is a member of the Bunyaviridae family of RNA viruses. Clinical disease is rare in...
and severe fever with thrombocytopenia syndrome
Severe fever with thrombocytopenia syndrome
Severe fever with thrombocytopenia syndrome is an emerging infectious disease recently discovered in northeast and central China. SFTS cause high fatality rate of 12% and as high as 30% in some areas...
.