''Betacoronavirus'' (β-CoVs or Beta-CoVs) is one of four genera (''

Alpha Alpha (uppercase , lowercase ; grc, ἄλφα, ''álpha'', or ell, άλφα, álfa) is the first letter of the Greek alphabet. In the system of Greek numerals, it has a value of one. Alpha is derived from the Phoenician letter aleph , whi ...

''-, ''Beta-'', '' Gamma-'', and '' Delta-'') of

coronavirus Coronaviruses are a group of related RNA viruses that cause diseases in mammals and birds. In humans and birds, they cause respiratory tract infections that can range from mild to lethal. Mild illnesses in humans include some cases of the co ...

es. Member viruses are enveloped, positive-strand RNA viruses that infect

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...

s (of which

human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...

s are part). The

natural reservoir In infectious disease ecology and epidemiology, a natural reservoir, also known as a disease reservoir or a reservoir of infection, is the population of organisms or the specific environment in which an infectious pathogen naturally lives and r ...

for betacoronaviruses are bats and rodents. Rodents are the reservoir for the subgenus '' Embecovirus'', while bats are the reservoir for the other subgenera. The coronavirus genera are each composed of varying viral lineages with the betacoronavirus genus containing four such lineages: A, B, C, D. In older literature, this genus is also known as "group 2 coronaviruses". The genus is in the subfamily ''

Orthocoronavirinae Coronaviruses are a group of related RNA viruses that cause diseases in mammals and birds. In humans and birds, they cause respiratory tract infections that can range from mild to lethal. Mild illnesses in humans include some cases of the c ...

'' in the family ''

Coronaviridae ''Coronaviridae'' is a family of enveloped, positive-strand RNA viruses which infect amphibians, birds, and mammals. The group includes the subfamilies '' Letovirinae'' and ''Orthocoronavirinae;'' the members of the latter are known as coronavi ...

'', of the order ''

Nidovirales ''Nidovirales'' is an order of enveloped, positive-strand RNA viruses which infect vertebrates and invertebrates. Host organisms include mammals, birds, reptiles, amphibians, fish, arthropods, molluscs, and helminths. The order includes the ...

''. The betacoronaviruses of the greatest clinical importance concerning humans are OC43 and HKU1 (which can cause the

common cold The common cold or the cold is a viral infectious disease of the upper respiratory tract that primarily affects the respiratory mucosa of the nose, throat, sinuses, and larynx. Signs and symptoms may appear fewer than two days after expos ...

) of lineage A, SARS-CoV and

SARS-CoV-2 Severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) is a strain of coronavirus that causes COVID-19 (coronavirus disease 2019), the respiratory illness responsible for the ongoing COVID-19 pandemic. The virus previously had a ...

(which has caused the disease

COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was identified in Wuhan, China, in December 2019. The disease quick ...

) of lineage B, and

MERS-CoV ''Middle East respiratory syndrome–related coronavirus'' (''MERS-CoV''), or EMC/2012 ( HCoV-EMC/2012), is the virus that causes Middle East respiratory syndrome (MERS). It is a species of coronavirus which infects humans, bats, and camels. Th ...

of lineage C. MERS-CoV is the first betacoronavirus belonging to lineage C that is known to infect humans.

Etymology

The name "betacoronavirus" is derived from

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic pe ...

βῆτα ('' bē̂ta'', "the second letter of the

Greek alphabet The Greek alphabet has been used to write the Greek language since the late 9th or early 8th century BCE. It is derived from the earlier Phoenician alphabet, and was the earliest known alphabetic script to have distinct letters for vowels as ...

"), and κορώνη (korṓnē, “garland, wreath”), meaning crown, which describes the appearance of the surface projections seen under electron microscopy that resemble a

solar corona A corona ( coronas or coronae) is the outermost layer of a star's atmosphere. It consists of plasma. The Sun's corona lies above the chromosphere and extends millions of kilometres into outer space. It is most easily seen during a total solar ...

. This morphology is created by the viral spike (S) peplomers, which are proteins that populate the surface of the virus and determine host tropism. The order ''

'' is named for the Latin ''

nidus Nidus may refer to: * Nidus (nest), for insects or small animals * The characteristic lesion in osteoid osteoma * The centre of a bladder stone * The material around which an enterolith An enterolith is a mineral concretion or calculus formed ...

'', which means 'nest'. It refers to this order's production of a 3′-coterminal nested set of subgenomic mRNAs during infection.

Structure

Several structures of the spike proteins have been resolved. The receptor binding domain in the alpha- and betacoronavirus spike protein is cataloged as . The spike protein, a type 1 fusion machine, assembles into a trimer (); its core structure resembles that of paramyxovirus F (fusion) proteins. The receptor usage is not very conserved; for example, among ''

Sarbecovirus ''Severe acute respiratory syndrome–related coronavirus'' (SARSr-CoV or SARS-CoV)The terms ''SARSr-CoV'' and ''SARS-CoV'' are sometimes used interchangeably, especially prior to the discovery of SARS-CoV-2. This may cause confusion when some ...

'', only a sub-lineage containing SARS share the

ACE2 Angiotensin-converting enzyme 2 (ACE2) is an enzyme that can be found either attached to the membrane of cells (mACE2) in the intestines, kidney, testis, gallbladder, and heart or in a soluble form (sACE2). Both membrane bound and soluble ACE2 ...

receptor. The viruses of subgenera ''Embecovirus'' differ from all others in the genus in that they have an additional shorter (8 nm) spike-like protein called hemagglutinin esterase (HE) (). It is believed to have been acquired from influenza C virus.

Genome

Coronaviruses have a large

genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ...

size that ranges from 26 to 32 kilobases. The overall structure of β-CoV genome is similar to that of other CoVs, with an

ORF1ab ORF1ab (also ORF1a/b) refers collectively to two open reading frames (ORFs), ORF1a and ORF1b, that are conserved in the genomes of nidoviruses, a group of viruses that includes coronaviruses. The genes express large polyproteins that undergo ...

replicase polyprotein (''rep'', ''pp1ab'') preceding other elements. This polyprotein is cleaved into 16 nonstructural proteins (see UniProt annotation of SARS ''rep'', ). As of May 2013,

GenBank The GenBank sequence database is an open access, annotated collection of all publicly available nucleotide sequences and their protein translations. It is produced and maintained by the National Center for Biotechnology Information (NCBI; a part ...

has 46 published complete genomes of the α- (group 1), β- (group 2), γ- (group 3), and δ- (group 4) CoVs.

Recombination

Genetic recombination Genetic recombination (also known as genetic reshuffling) is the exchange of genetic material between different organisms which leads to production of offspring with combinations of traits that differ from those found in either parent. In eukaryo ...

can occur when two or more viral

s are present in the same host cell. The

dromedary The dromedary (''Camelus dromedarius'' or ;), also known as the dromedary camel, Arabian camel, or one-humped camel, is a large even-toed ungulate, of the genus '' Camelus'', with one hump on its back. It is the tallest of the three species o ...

camel Beta-CoV HKU23 exhibits genetic diversity in the African camel population.Diversity of Dromedary Camel Coronavirus HKU23 in African Camels Revealed Multiple Recombination Events among Closely Related Betacoronaviruses of the Subgenus Embecovirus. So RTY, et al. J Virol. 2019. Contributing to this diversity are several recombination events that had taken place in the past between closely related betacoronaviruses of the subgenus ''Embecovirus''. Also the betacoronavirus, Human SARS-CoV, appears to have had a complex history of recombination between ancestral

es that were hosted in several different animal groups.Zhang XW, Yap YL, Danchin A. Testing the hypothesis of a recombinant origin of the SARS-associated coronavirus. Arch Virol. 2005 Jan;150(1):1-20. Epub 2004 Oct 11.

Pathogenesis

Alpha- and betacoronaviruses mainly infect bats, but they also infect other species like

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camels A camel (from: la, camelus and grc-gre, κάμηλος (''kamēlos'') from Hebrew or Phoenician: גָמָל ''gāmāl''.) is an even-toed ungulate in the genus ''Camelus'' that bears distinctive fatty deposits known as "humps" on its back. ...

, and

rodents Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...

. Betacoronaviruses that have caused epidemics in humans generally induce fever and respiratory symptoms. They include: * SARS-CoV, causing

SARS Severe acute respiratory syndrome (SARS) is a viral respiratory disease of zoonotic origin caused by the severe acute respiratory syndrome coronavirus (SARS-CoV or SARS-CoV-1), the first identified strain of the SARS coronavirus species, ''seve ...

. *

, causing MERS. *

, causing

Classification

Within the genus ''Betacoronavirus'' (Group 2 CoV), four subgenera or lineages (A, B, C, and D) have traditionally been recognized. The four lineages have also been named using Greek letters or numerically. A fifth subgenus, ''Hibecovirus'', was added more recently. Member subgenera and species include:

''Embecovirus'' (lineage A)

'' Betacoronavirus 1'' * Bovine coronavirus * Human coronavirus OC43 ''

China Rattus coronavirus HKU24 ''China Rattus coronavirus HKU24'' is a species of coronavirus in the genus ''Betacoronavirus ''Betacoronavirus'' (β-CoVs or Beta-CoVs) is one of four genera ('' Alpha''-, ''Beta-'', '' Gamma-'', and '' Delta-'') of coronaviruses. Member ...

''
'' Human coronavirus HKU1''
'' Murine coronavirus'' * Mouse hepatitis virus ''

Myodes coronavirus 2JL14 ''Myodes coronavirus 2JL14'' is a species of coronavirus in the genus ''Betacoronavirus ''Betacoronavirus'' (β-CoVs or Beta-CoVs) is one of four genera ('' Alpha''-, ''Beta-'', '' Gamma-'', and '' Delta-'') of coronaviruses. Member viruse ...

''Sarbecovirus'' (lineage B)

'' Severe acute respiratory syndrome–related coronavirus (SARSr-CoV or SARS-CoV)'' * Severe acute respiratory syndrome coronavirus (SARS-CoV or SARS-CoV-1) * Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) * Bat SARS-like coronavirus WIV1 (Bat SL-CoV-WIV1) * Bat coronavirus RaTG13

''Merbecovirus'' (lineage C)

Hedgehog coronavirus 1 ''Hedgehog coronavirus 1'' is a mammalian Group C '' Betacoronavirus'', a positive-sense RNA virus, discovered in European hedgehogs (''Erinaceus europaeus'') from Germany and first described in 2014. Most ''Betacoronavirus'' clade c viruses are ...

''
'' Middle East respiratory syndrome-related coronavirus (MERS-CoV)''
''

Pipistrellus bat coronavirus HKU5 ''Pipistrellus bat coronavirus HKU5'' (''Bat-CoV HKU5'') is an enveloped, positive-sense single-stranded RNA mammalian Group 2 '' Betacoronavirus'' discovered in Japanese ''Pipistrellus'' in Hong Kong. This strain of coronavirus is closely relat ...

''
'' Tylonycteris bat coronavirus HKU4''

''Nobecovirus'' (lineage D)

Eidolon bat coronavirus C704 ''Eidolon bat coronavirus C704'' is a species of coronavirus in the genus ''Betacoronavirus ''Betacoronavirus'' (β-CoVs or Beta-CoVs) is one of four genera ('' Alpha''-, ''Beta-'', '' Gamma-'', and '' Delta-'') of coronaviruses. Member vi ...

''
''

Rousettus bat coronavirus GCCDC1 ''Rousettus bat coronavirus GCCDC1'' is a species of coronavirus in the genus ''Betacoronavirus ''Betacoronavirus'' (β-CoVs or Beta-CoVs) is one of four genera ('' Alpha''-, ''Beta-'', '' Gamma-'', and '' Delta-'') of coronaviruses. Membe ...

''
''

Rousettus bat coronavirus HKU9 ''Rousettus bat coronavirus HKU9'' (''HKU9-1'') is an enveloped, positive-sense, single-stranded RNA mammalian Group 2 ''Betacoronavirus'' discovered in ''Rousettus'' bats in China in 2011. This strain of coronavirus is closely related to the EM ...

''Hibecovirus''

'' Bat Hp-betacoronavirus Zhejiang2013''

References

External links

Coronaviruses

Virus Pathogen Database and Analysis Resource (ViPR): ''Coronaviridae''
{{Taxonbar, from=Q16532287 Virus genera Coronaviruses