View source for Bunyaviricetes

{{Short description|Order of RNA viruses}}
{{Virusbox
| image = Viruses-08-00106-g001.png
| image_alt =
| image_caption = [[Crimean-Congo hemorrhagic fever virus]] (CCHFV) virion and replication cycle
| taxon = Bunyaviricetes
| display_parents = 2
| subdivision_ranks = Subtaxa
| subdivision_ref =
| subdivision = *[[#Taxonomy|See text]]
}}

'''''Bunyaviricetes''''' is a class of segmented [[negative-strand RNA virus]]es with mainly tripartite genomes. Member viruses infect [[arthropod]]s, [[plant]]s, [[protozoa]]ns, and [[vertebrate]]s.<ref name=":0">{{Cite journal|last1=Herath|first1=Venura|last2=Romay|first2=Gustavo|last3=Urrutia|first3=Cesar D.|last4=Verchot|first4=Jeanmarie|date=September 2020|title=Family Level Phylogenies Reveal Relationships of Plant Viruses within the Order Bunyavirales|journal=Viruses|language=en|volume=12|issue=9|pages=1010|doi=10.3390/v12091010|pmid=32927652|pmc=7551631|doi-access=free}}</ref> The name ''Bunyaviricetes'' derives from [[Bunyamwera]],<ref name="ICTV9">{{cite web |title=ICTV 9th Report (2011) ''Bunyaviridae'' |url=https://ictv.global/report/chapter/peribunyaviridae |website=International Committee on Taxonomy of Viruses (ICTV) |access-date=31 January 2019 |language=en |quote=Bunya: from Bunyamwera, place in Uganda, where type virus was isolated.}}</ref> where the virus [[Bunyamwera virus]] was first discovered.<ref name="Smithburn">{{cite journal |last1=Smithburn |first1=K. C. |last2=Haddow |first2=A. J. |last3=Mahaffy |first3=A. F. |title=A Neurotropic Virus Isolated from Aedes Mosquitoes Caught in the Semliki Forest |journal=The American Journal of Tropical Medicine and Hygiene |date=March 1946 |volume=s1-26 |issue=2 |pages=189–208 |doi=10.4269/ajtmh.1946.s1-26.189 |pmid=21020339 |language=en |issn=1476-1645 |oclc=677158400}}</ref>

Bunyaviruses belong to the fifth group of the [[Baltimore classification|Baltimore classification system]], which includes viruses with a [[Sense (molecular biology)|negative-sense]], single-stranded RNA genome.  They have an [[Viral envelope|enveloped]], spherical virion. Though generally found in [[arthropod]]s or rodents, certain viruses in this class occasionally infect humans. Some of them also infect plants.<ref name= PlyusninAElliottRM>{{cite book |editor1=Plyusnin, A |editor2=Elliott, RM | year=2011 | title=Bunyaviridae: Molecular and Cellular Biology | publisher=[[Caister Academic Press]] | isbn= 978-1-904455-90-5}}</ref> In addition, there is a group of bunyaviruses whose replication is restricted to arthropods and is known as insect-specific bunyaviruses.<ref>{{Cite journal|last1=Elrefaey|first1=Ahmed ME|last2=Abdelnabi|first2=Rana|last3=Rosales Rosas|first3=Ana Lucia|last4=Wang|first4=Lanjiao|last5=Basu|first5=Sanjay|last6=Delang|first6=Leen|date=September 2020|title=Understanding the Mechanisms Underlying Host Restriction of Insect-Specific Viruses|journal=Viruses|language=en|volume=12|issue=9|pages=964|doi=10.3390/v12090964|pmid=32878245|pmc=7552076|doi-access=free}}</ref>

A majority of bunyaviruses are vector-borne. With the exception of [[Hantaviruses]] and [[Arenavirus]]es, all viruses in the ''Bunyaviricetes'' class are [[Arbovirus|transmitted by arthropods]] (mosquitos, tick, or sandfly). Hantaviruses are transmitted through contact with [[rodent]] feces. Incidence of infection is closely linked to vector activity, for example, mosquito-borne viruses are more common in the summer.<ref name="PlyusninAElliottRM" />

Human infections with certain members of ''Bunyaviricetes'', such as [[Crimean-Congo hemorrhagic fever virus]], are associated with high levels of morbidity and mortality, consequently handling of these viruses is done in [[biosafety level 4]] laboratories. They are also the cause of [[severe fever with thrombocytopenia syndrome]].<ref name="nejm">{{cite journal |vauthors=Yu XJ, Liang MF, Zhang SY |title=Fever with thrombocytopenia associated with a novel bunyavirus in China |journal=N. Engl. J. Med. |volume=364 |issue=16 |pages=1523–32 |date=April 2011 |pmid=21410387 |pmc=3113718 |doi=10.1056/NEJMoa1010095 |display-authors=etal}}</ref>

[[Hantavirus]]es  are another medically important member of the class ''Bunyaviricetes''. They are found worldwide, and are relatively common in [[Korea]], [[Scandinavia]] (including [[Finland]]), [[Russia]], western North America and parts of South America. Hantavirus infections are associated with high fever, lung edema, and pulmonary failure. The mortality rate varies significantly depending on the form, being up to 50% in New World hantaviruses (the Americas), up to 15% in Old World hantaviruses (Asia and Europe), and as little as 0.1% in [[Puumala virus]] (mostly Scandinavia).<ref>{{cite journal | author1=Walter Muranyi | author2=Udo Bahr | author3=Martin Zeier | author4=Fokko J. van der Woude | year=2005 | title=Hantavirus Infection | journal=Journal of the American Society of Nephrology | volume=16 | issue=12 |pages=3669–3679 | doi=10.1681/ASN.2005050561  | pmid=16267154 | doi-access=free }}</ref> The antibody reaction plays an important role in decreasing levels of [[viremia]].

== Virology ==
=== Structure ===
[[File:Peribunyavirus virion structure.gif|thumb|Peribunyavirus virion structure]]
Bunyavirus [[morphology (biology)|morphology]] is somewhat similar to that of the ''[[Paramyxoviridae]]'' family; bunyaviruses form enveloped, spherical virions with diameters of 80–120 [[nanometer|nm]]. These viruses contain no matrix proteins.<ref>{{Cite web|title=Bunyaviridae - Negative Sense RNA Viruses - Negative Sense RNA Viruses (2011)|url=https://ictv.global/report/chapter/peribunyaviridae|access-date=2020-09-08|website=International Committee on Taxonomy of Viruses (ICTV)|language=en}}</ref> Instead, the viral surface glycoproteins which form a continuous layer on the virion surface are thought to play a role in the formation of new virions by budding from a cell membrane.<ref name="pmid20219926">{{cite journal| author=Huiskonen JT, Hepojoki J, Laurinmäki P, Vaheri A, Lankinen H, Butcher SJ | display-authors=etal| title=Electron cryotomography of Tula hantavirus suggests a unique assembly paradigm for enveloped viruses. | journal=J Virol | year= 2010 | volume= 84 | issue= 10 | pages= 4889–97 | pmid=20219926 | doi=10.1128/JVI.00057-10 | pmc=2863824 }} </ref> 

=== Genome ===
Bunyaviruses have bi- or tripartite [[genome]]s consisting of a large (L) and small(s), or 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{{Citation needed|date=February 2025}} 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).<ref>{{Cite journal|last1=Ariza|first1=A.|last2=Tanner|first2=S. J.|last3=Walter|first3=C. T.|last4=Dent|first4=K. C.|last5=Shepherd|first5=D. A.|last6=Wu|first6=W.|last7=Matthews|first7=S. V.|last8=Hiscox|first8=J. A.|last9=Green|first9=T. J.|date=2013-06-01|title=Nucleocapsid protein structures from orthobunyaviruses reveal insight into ribonucleoprotein architecture and RNA polymerization|journal=Nucleic Acids Research|volume=41|issue=11|pages=5912–5926|doi=10.1093/nar/gkt268|issn=0305-1048|pmc=3675483|pmid=23595147}}</ref>

Most bunyaviruses have a negative-sense L and M segment. The S segment of the genus ''[[Phlebovirus]]'',<ref name="phlebovirus">{{cite journal |last1=Elliott |first1=Richard M |last2=Brennan |first2=Benjamin |title=Emerging phleboviruses |journal=Current Opinion in Virology |date=April 2014 |volume=5 |issue=100 |pages=50–57 |doi=10.1016/j.coviro.2014.01.011|pmid=24607799 |pmc=4031632 }}</ref> and both M and S segment of the genus ''[[Tospovirus]]'' are [[ambisense]].<ref name="tospovirus">{{cite journal |last1=Lima |first1=R. N. |last2=De Oliveira |first2=A. S. |last3=Leastro |first3=M. O. |last4=Blawid |first4=R. |last5=Nagata |first5=T. |last6=Resende |first6=R. O. |last7=Melo |first7=F. L. |title=The complete genome of the tospovirus Zucchini lethal chlorosis virus |journal=Virology Journal |date=7 July 2016 |volume=13 |issue=1 |pages=123 |doi=10.1186/s12985-016-0577-4|pmid=27388209 |pmc=4936248 |doi-access=free }}</ref> Ambisense means that some of the genes on the RNA strand are negative sense and others are positive sense. The ambisense S segment codes for the viral [[nucleoprotein]] (N) in the negative sense and a [[Bunyaviridae nonstructural S proteins|nonstructural protein]] (NSs) in the positive sense. The ambisense M segment codes for [[glycoprotein]] (GP) in the negative sense and a nonstructural protein (NSm) in the positive sense.<ref name="tospovirus" />

The total genome size ranges from 10.5 to 22.7 [[kilo base pair|kbp]].<ref name="ICTVdb">{{cite web |url=https://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/00.011.htm |publisher=ICTVdB—The Universal Virus Database, version 4 |title=00.011. ''Bunyaviridae'' |year=2006 |access-date=2009-01-01}}</ref>

=== Life cycle ===
[[File:ONSR.Nairo.Fig3.v2 WEB.png|thumb|Nairovirus life cycle]]
The ambisense genome 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 RNA to produce viral genomes.{{cn|date=October 2022}}

Bunyaviruses replicate in the [[cytoplasm]], while the viral proteins transit through the [[endoplasmic reticulum|ER]] and [[Golgi apparatus]]. Mature virions bud from the Golgi apparatus into vesicles which are transported to the cell surface.{{cn|date=October 2022}}

=== Transmission ===
Bunyaviruses infect [[arthropod]]s, [[plant]]s, [[protozoa]]ns, and [[vertebrate]]s.<ref name=":0" /> Plants can host bunyaviruses from the families ''Tospoviridae'' and ''Fimoviridae'' (e.g. tomato, pigeonpea, melon, wheat, raspberry, redbud, and rose). Members of some families are insect-specific, for example the phasmavirids, first isolated from [[Chaoboridae|phantom midges]],<ref name="Ballinger2014">{{cite journal|last1=Ballinger|first1=MJ|last2=Bruenn|first2=JA|last3=Hay|first3=J|last4=Czechowski|first4=D|last5=Taylor|first5=DJ|year=2014|title=Discovery and evolution of bunyavirids in arctic phantom midges and ancient bunyavirid-like sequences in insect genomes|journal=J Virol|volume=88|issue=16|pages=8783–94|doi=10.1128/JVI.00531-14|pmc=4136290|pmid=24850747}}</ref> and since identified in diverse insects including [[Lepidoptera|moths]], [[Apoidea|wasps and bees]], and other [[Diptera|true flies]].

== Taxonomy ==
[[File:Viruses-12-01010-g001-pdf-crop.jpg|thumb|Phylogenetic tree of ''Bunyaviricetes'']]
The class ''Bunyaviricetes'' contains two orders which contain 16 families. These taxa are listed hereafter (-''virales'' denotes order and -''viridae'' denotes family):<ref>{{cite web|title=Virus Taxonomy: 2024 Release|url=https://ictv.global/taxonomy|publisher=International Committee on Taxonomy of Viruses|access-date=17 March 2025}}</ref>

{{div col}}
* ''[[Elliovirales]]''
** ''[[Cruliviridae]]''
** ''[[Fimoviridae]]''
** ''[[Hantaviridae]]''
** ''[[Peribunyaviridae]]''
** ''[[Phasmaviridae]]''
** ''[[Tospoviridae]]''
** ''[[Tulasviridae]]''
* ''[[Hareavirales]]''
** ''[[Arenaviridae]]''
** ''[[Discoviridae]]''
** ''[[Konkoviridae]]''
** ''[[Leishbuviridae]]''
** ''[[Mypoviridae]]''
** ''[[Nairoviridae]]''
** ''[[Phenuiviridae]]''
** ''[[Tosoviridae]]''
** ''[[Wupedeviridae]]''
{{div col end}}

==Diseases in humans==
Bunyaviruses that cause disease in humans include:
* [[California encephalitis virus]], [[Jamestown Canyon virus]], [[La Crosse encephalitis virus]], [[Oropouche virus]], and [[Snowshoe hare virus]]  (vector: mosquitoes; family: ''Peribunyaviridae'');
* [[Hantavirus]] reservoir: small mammals or rodents (vector: aerosolized excreta from these mammals; family: ''Hantaviridae'');
* [[Crimean–Congo hemorrhagic fever]] reservoir and (vector: ticks; amplifying hosts and vector: small mammals, domestic mammals; family: ''[[Nairoviridae]]'');
* [[Rift Valley fever]] (reservoir: bats; vector: mosquitoes; amplifying hosts: small and domestic mammals; family: ''[[Phenuiviridae]]'');
* [[Bwamba Fever]] (reservoir: monkeys; vector: mosquitoes; amplifying hosts: donkeys; family: ''Peribunyaviridae'');
* [[Severe fever with thrombocytopenia syndrome]] (vector: ticks);
* [[Lassa fever]] and [[Argentine hemorrhagic fever]] (reservoir: rodents; vector: aerosolized excreta from these mammals; family: ''Arenaviridae'').

Bunyaviruses have segmented genomes, making them capable of rapid reassortment and increasing the risk of outbreak.<ref>{{Citation| doi = 10.1016/j.virol.2013.07.030| title = Viruses of the family Bunyaviridae: Are all available isolates reassortants?| date = November 2013| last1 = Briese| first1 = Thomas| last2 = Calisher| first2 = Charles H.| last3 = Higgs| first3 = Stephen| journal = Virology| volume = 446| issue = 1–2| pages = 207–216| pmid = 24074583| hdl = 2097/17679| hdl-access = free}}</ref><ref>{{Cite journal| doi = 10.3390/v6114373| issn = 1999-4915| volume = 6| issue = 11| pages = 4373–4397| last1 = Horne| first1 = Kate McElroy| last2 = Vanlandingham| first2 = Dana L.| title = Bunyavirus-Vector Interactions| journal = Viruses| date = 2014-11-13| pmid = 25402172| pmc = 4246228| doi-access = free}}</ref>  The bunyavirus that causes [[severe fever with thrombocytopenia syndrome]] can undergo recombination both by reassortment of [[genome]] segments and by intragenic [[homologous recombination]].<ref>Lv Q, Zhang H, Tian L, Zhang R, Zhang Z, Li J, Tong Y, Fan H, Carr MJ, Shi W.  Novel sub-lineages, recombinants and reassortants of severe fever with thrombocytopenia syndrome virus.  Ticks Tick Borne Dis. 2017 Mar;8(3):385-390. doi: 10.1016/j.ttbdis.2016.12.015. Epub 2017 Jan 3. {{PMID|28117273}}</ref><ref>He CQ, Ding NZ.  Discovery of severe fever with thrombocytopenia syndrome bunyavirus strains originating from intragenic recombination.  J Virol. 2012 Nov;86(22):12426-30. doi: 10.1128/JVI.01317-12. Epub 2012 Aug 29.  {{PMID|22933273}}</ref> Bunyaviruses are transmitted by hematophagous arthropods including mosquitoes, midges, flies, and ticks. The viral incubation period is about 48 hours.  Symptomatic infection typically causes non-specific [[flu-like]] symptoms with fever lasting for about three days.  Because of their [[non-specific symptoms]], Bunyavirus infections are frequently mistaken for other illnesses.  For example, Bwamba fever is often mistaken for malaria.<ref>{{Cite book| edition = 6| publisher = Mosby| isbn = 9780323054706| author = Patrick R. Murray, Ken S. Rosenthal and Michael A. Pfaller|title = Medical Microbiology, 6e| location = Philadelphia| date = 2008-12-24}}</ref>

==Prevention==
Prevention depends on the reservoir, amplifying hosts and how the viruses are transmitted, i.e. the vector, whether ticks or mosquitoes and which animals are involved. Preventive measures include general hygiene, limiting contact with vector saliva, urine, feces, or bedding. There is no licensed vaccine for bunyaviruses. As precautions Cache Valley virus and Hantavirus research are conducted in BSL-2 (or higher), Rift Valley Fever virus research is conducted in BSL-3 (or higher), Congo-Crimean Hemorrhagic Fever virus research is conducted in BSL-4 laboratories.{{cn|date=October 2022}}

==Timeline==
'''1940s:''' [[Crimean–Congo hemorrhagic fever]] is discovered in [[Russia]]

'''1951:''' 3,000 cases of [[Hantavirus]] were reported in South Korea in 1951, a time when UN forces were fighting on the 38th parallel during the Korean War

'''1956:''' [[Cache Valley virus]] isolated in ''[[Culiseta inornata]]'' mosquitoes in Utah

'''1960:''' [[La Crosse virus]] was first recognized in a fatal case of encephalitis in [[La Crosse, Wisconsin]]

'''1977:''' [[Rift Valley Fever]] virus caused approximately 200,000 cases and 598 deaths in [[Egypt]]

'''2017:''' ''Bunyavirales'' order is created.

== References ==
{{Reflist|2}}

== External links ==
* [http://www.expasy.org/viralzone/all_by_species/82.html '''Viralzone''': Bunyaviridae]
* [https://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/00.011.htm ICTVdb Index of Viruses—''Bunyaviridae'']
* [http://www.virology.net/Big_Virology/BVRNAbunya.html The Big Picture Book of Viruses: ''Bunyaviridae''] {{Webarchive|url=https://web.archive.org/web/20160511185402/http://www.virology.net/Big_Virology/BVRNAbunya.html |date=2016-05-11 }}
* [https://web.archive.org/web/20151007112957/http://vbrc.org/query.asp?web_taxonomy=Bunyaviridae Bunyaviridae Genomes]—database search results from the [http://www.vbrc.org/ Viral Bioinformatics Resource Center]
* [https://www.viprbrc.org/brc/home.spg?decorator=vipr# Virus Pathogen Database and Analysis Resource (ViPR): Bunyaviridae]
* {{cite web |title=''Bunyaviridae'' |work=NCBI Taxonomy Browser |url=https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=11571 |id=11571}}

{{Zoonotic viral diseases}}
{{Baltimore_(virus_classification)}}
{{Taxonbar|from=Q29000551}}
{{Authority control}}

[[Category:Bunyavirales| ]]
[[Category:Hemorrhagic fevers]]
[[Category:Virus classes]]