Nairovirus
Encyclopedia
Nairovirus 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. Viruses in this genus are tick-borne viruses that can have human or animal hosts.
Other viruses in this genus include:
Crimean-Congo hemorrhagic fever virus (CCHFV)
Dera Ghazi Khan virus (DGKV)
Dugbe virus (DUGV)
Hughes virus (HUGV)
Qalyub virus
(QYBV)
Sakhalin virus (SAKV)
Thiafora virus (TFAV)
The genus is divided into a number (at least seven) serogroups:
Crimean-Congo hemorrhagic fever
Dera Ghazi Khan
Hughes
Nairobi sheep disease
Qalyub
Sakhalin
Thiafora
Within each serogroup are a number of related viruses:
Crimean-Congo hemorrhagic fever serogroup:
Dera Ghazi Khan serogroup:
Hughes serogroup:
Nairobi sheep disease serogroup:
Qalyub serogroup:
Sakhalin serogroup:
Thiafora serogroup:
ic, segmented, circular, negative sense, single-stranded RNA. The complete genome
is about 17,100-22,800 nucleotide
s long and is segmented into three segments: large, medium, and small. The large segment is about 11000-14400 nucleotides long (6.8–12 kb) and it encodes for the nucleocapsid protein. The medium segment is about 4,400-6,300 nucleotides long (3.2-4.9kb) and it encodes for glycoprotein
s G¬n and Gc. The small segment is about 1,700-2,100 nucleotides long (1-3kb) and it encodes the viral polymerase.
The genome has terminally redundant sequences with the sequences being repeated at both ends. The terminal nucleotides are base-paired forming non-covalently closed, circular RNA. Both the 5’ and 3’ end have conserved regions of 9 nucleotides in length. The sequences are 5’end UCUCAAAGA and 3’end AGAGUUUCU.
These nucleocapsids are surrounded by a single envelope that has projections made of glycoproteins protruding from its surface. These projections evenly cover the surface of the virion and are about 5-10 nm long. They aid in attachment to the host receptor in replication
.
. They attach to the host receptors by their Gn-Gc glycoprotein dimer. The virus is then endocytosed
into the host cell via a vesicle
. The ribonucleocapsid segments are released into the cytoplasm
commencing transcription
. Transcription and replication occur in the cell and the newly synthesized virions are released by budding
.
hosts
and is transmitted via insects such as ticks and flies.
There are no geographical localizations of this virus. It is widespread. However, the Crimean-Congo hemorrhagic fever virus is localized to Africa
, Asia
and Europe
.
Bunyaviridae
Bunyaviridae is a family of negative-stranded RNA viruses. Though generally found in arthropods or rodents, certain viruses in this family occasionally infect humans. Some of them also infect plants....
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. Viruses in this genus are tick-borne viruses that can have human or animal hosts.
Taxonomy
The Nairobi sheep disease virus (NSD) is the prototype virus of the genus. This virus is found in East and Central Africa and causes acute hemorrhagic gastroenteritis in sheep and goats. There are 34 viruses currently recognised in this genus. All are tick borne.Other viruses in this genus include:
Crimean-Congo hemorrhagic fever virus (CCHFV)
Dera Ghazi Khan virus (DGKV)
Dugbe virus (DUGV)
Hughes virus (HUGV)
Qalyub virus
Qalyub virus
Qalyub virus is a nairovirus discovered in a rat's nest in a tomb wall in the Egyptian town of Qalyub in 1952. The primary vector for transmission is the Ornithodoros erraticus tick, and thus it is an arbovirus....
(QYBV)
Sakhalin virus (SAKV)
Thiafora virus (TFAV)
The genus is divided into a number (at least seven) serogroups:
Crimean-Congo hemorrhagic fever
Dera Ghazi Khan
Hughes
Nairobi sheep disease
Qalyub
Sakhalin
Thiafora
Within each serogroup are a number of related viruses:
Crimean-Congo hemorrhagic fever serogroup:
- Crimean-Congo hemorrhagic fever virus
- Hazara virus
Dera Ghazi Khan serogroup:
- Abu Hammad virus
- Abu Mina virus
Hughes serogroup:
- Fallalon virus
- Hughes virus
- Punte Salinas virus
- Raza virus
Nairobi sheep disease serogroup:
- Nairobi sheep disease virus
- Ganjam virus
- Dugbe virus
- Kupe virus
Qalyub serogroup:
- Bandia virus
- Qalyub virus
Sakhalin serogroup:
- Sakhalin virus
- Tillamok virus
Thiafora serogroup:
- Erve virus
- Thiafora virus
Genome
Nairovirus genomes are monomerMonomer
A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer; the term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex...
ic, segmented, circular, negative sense, single-stranded RNA. The complete genome
Genome
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....
is about 17,100-22,800 nucleotide
Nucleotide
Nucleotides are molecules that, when joined together, make up the structural units of RNA and DNA. In addition, nucleotides participate in cellular signaling , and are incorporated into important cofactors of enzymatic reactions...
s long and is segmented into three segments: large, medium, and small. The large segment is about 11000-14400 nucleotides long (6.8–12 kb) and it encodes for the nucleocapsid protein. The medium segment is about 4,400-6,300 nucleotides long (3.2-4.9kb) and it encodes for 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 G¬n and Gc. The small segment is about 1,700-2,100 nucleotides long (1-3kb) and it encodes the viral polymerase.
The genome has terminally redundant sequences with the sequences being repeated at both ends. The terminal nucleotides are base-paired forming non-covalently closed, circular RNA. Both the 5’ and 3’ end have conserved regions of 9 nucleotides in length. The sequences are 5’end UCUCAAAGA and 3’end AGAGUUUCU.
Virion
The virions for viruses in this genus have a spherical shape. They range in size from about 80-120 nm in diameter with 50% of their weight attributed to proteins and 20-30% of their weight attributed to lipids. The virions have 3 non-segmented, circular, symmetric nucleocapsids. The ribonucleocapsid is filamentous and has a length of about 200-300 nm and a width of about 2-2.5 nm.These nucleocapsids are surrounded by a single envelope that has projections made of glycoproteins protruding from its surface. These projections evenly cover the surface of the virion and are about 5-10 nm long. They aid in attachment to the host receptor in replication
DNA replication
DNA replication is a biological process that occurs in all living organisms and copies their DNA; it is the basis for biological inheritance. The process starts with one double-stranded DNA molecule and produces two identical copies of the molecule...
.
Replication
These viruses are not dependent on a helper virusHelper virus
A helper virus is a virus used when producing copies of a helper dependent viral vector which does not have the ability to replicate on its own. The helper virus is used to coinfect cells alongside the viral vector and provides the necessary enzymes for replication of the genome of the viral vector....
. They attach to the host receptors by their Gn-Gc glycoprotein dimer. The virus is then endocytosed
Endocytosis
Endocytosis is a process by which cells absorb molecules by engulfing them. It is used by all cells of the body because most substances important to them are large polar molecules that cannot pass through the hydrophobic plasma or cell membrane...
into the host cell via a vesicle
Vesicle (biology)
A vesicle is a bubble of liquid within another liquid, a supramolecular assembly made up of many different molecules. More technically, a vesicle is a small membrane-enclosed sack that can store or transport substances. Vesicles can form naturally because of the properties of lipid membranes , or...
. The ribonucleocapsid segments are released into 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...
commencing transcription
Transcription (genetics)
Transcription is the process of creating a complementary RNA copy of a sequence of DNA. Both RNA and DNA are nucleic acids, which use base pairs of nucleotides as a complementary language that can be converted back and forth from DNA to RNA by the action of the correct enzymes...
. Transcription and replication occur in the cell and the newly synthesized virions are released by budding
Budding
Budding is a form of asexual reproduction in which a new organism grows on another one. The new organism remains attached as it grows, separating from the parent organism only when it is mature. Since the reproduction is asexual, the newly created organism is a clone and is genetically identical...
.
Transmission & Distribution
This virus infects many different vertebrateVertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
hosts
Host (biology)
In biology, a host is an organism that harbors a parasite, or a mutual or commensal symbiont, typically providing nourishment and shelter. In botany, a host plant is one that supplies food resources and substrate for certain insects or other fauna...
and is transmitted via insects such as ticks and flies.
There are no geographical localizations of this virus. It is widespread. However, the Crimean-Congo hemorrhagic fever virus is localized to Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
, Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
and Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
.