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

Alpha Alpha (uppercase , lowercase ) 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'' , whose name comes from the West Semitic word for ' ...

''-, ''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 comm ...

es. Member viruses are enveloped,

positive-strand RNA virus Positive-strand RNA viruses (+ssRNA viruses) are a group of related viruses that have Sense (molecular biology), positive-sense, single-stranded genomes made of ribonucleic acid. The positive-sense genome can act as messenger RNA (mRNA) and can ...

es that infect

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

s, including

human Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...

s. The

natural reservoir In Infection, 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 li ...

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 co ...

'' in the family ''

Coronaviridae ''Coronaviridae'' is a family (biology), family of Viral envelope, enveloped, positive-strand RNA viruses which infect fish, amphibians, birds, and mammals. The group includes the subfamilies ''Letovirinae,'' ''Orthocoronavirinae'', and ''Pitovir ...

'', of the order '' Nidovirales''. 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 virus, viral infectious disease of the upper respiratory tract that primarily affects the Respiratory epithelium, respiratory mucosa of the human nose, nose, throat, Paranasal sinuses, sinuses, and larynx. ...

) of lineage A,

SARS-CoV-1 Severe acute respiratory syndrome coronavirus 1 (SARS-CoV-1), previously known as severe acute respiratory syndrome coronavirus (SARS-CoV), is a strain (biology), strain of coronavirus that causes severe acute respiratory syndrome (SARS), the ...

and

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

(the causes of

SARS Severe acute respiratory syndrome (SARS) is a viral respiratory disease of zoonotic origin caused by the virus SARS-CoV-1, the first identified strain of the SARS-related coronavirus. The first known cases occurred in November 2002, and the ...

and

COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by the coronavirus SARS-CoV-2. In January 2020, the disease spread worldwide, resulting in the COVID-19 pandemic. The symptoms of COVID‑19 can vary but often include fever ...

respectively) of lineage B, and MERS-CoV (the cause of

MERS Middle East respiratory syndrome (MERS) is a viral respiratory infection caused by '' Middle East respiratory syndrome–related coronavirus'' (MERS-CoV). Symptoms may range from none, to mild, to severe depending on age and risk level. Typi ...

) 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 classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

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 BC. It was derived from the earlier Phoenician alphabet, and is the earliest known alphabetic script to systematically write vowels as wel ...

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

solar corona In astronomy, a corona (: coronas or coronae) is the outermost layer of a star's Stellar atmosphere, atmosphere. It is a hot but relatively luminosity, dim region of Plasma (physics), plasma populated by intermittent coronal structures such as so ...

. This

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

is created by the viral spike (S)

peplomer In virology, a spike protein or peplomer protein is a protein that forms a large structure known as a spike or peplomer projecting from the surface of an enveloped virus. as cited in The proteins are usually glycoproteins that form dimers ...

s, which are proteins that populate the surface of the virus and determine host tropism. The order '' Nidovirales'' is named for the Latin '' nidus'', 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'', only a sub-lineage containing SARS share the 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 Influenza C virus is the only species in the genus ''Gammainfluenzavirus'', in the virus family '' Orthomyxoviridae'', which like other influenza viruses, causes influenza. Influenza C viruses are known to infect humans and pigs. Flu due to t ...

Genome

Coronaviruses have a large

genome 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 genes, other functional regions of the genome such as ...

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 replicase polyprotein (''rep'', ''pp1ab'') preceding other elements. This polyprotein is cleaved into 16

nonstructural protein In virology, a nonstructural protein is a protein encoded by a virus but that is not part of the viral particle. They typically include the various enzymes and transcription factors the virus uses to replicate itself, such as a viral protease ( 3CL ...

s (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 par ...

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 eukaryot ...

can occur when two or more viral

s are present in the same host cell. The

dromedary The dromedary (''Camelus dromedarius''), also known as the dromedary camel, Arabian camel and one-humped camel, is a large camel of the genus '' Camelus'' with one hump on its back. It is the tallest of the three camel species; adult males sta ...

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

humans Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...

, camels, 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 n ...

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

. * MERS-CoV, causing

. *

, 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: * Subgenus '' Embecovirus'' (lineage A) ** ''Betacoronavirus gravedinis'',

Human coronavirus OC43 Human coronavirus OC43 (HCoV-OC43) is a member of the species ''Betacoronavirus 1, Betacoronavirus gravedinis'', which infects humans and cattle. The infecting coronavirus is an Viral envelope, enveloped, Sense (molecular biology), positive-sense ...

Bovine coronavirus Bovine coronavirus (BCV or BCoV) is a coronavirus which is a member of the species '' Betacoronavirus gravedinis''. The infecting virus is an enveloped, positive-sense, single-stranded RNA virus which enters its host cell by binding to the ...

** ''Betacoronavirus hongkongense'',

Human coronavirus HKU1 Human coronavirus HKU1 (HCoV-HKU1, ''Betacoronavirus hongkonense'') is a species of coronavirus in humans and animals. It causes an upper respiratory disease with symptoms of the common cold, but can advance to pneumonia and bronchiolitis. It was ...

References

External links

Coronaviruses

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