WHO Director-General Tedros Adhanom Ghebreyesus (R), flanked by World Health Organization (WHO) Health Emergencies Programme head Michael Ryan (L), speaks during a press conference following a WHO Emergency committee to discuss whether the Coronavirus, the SARS-like virus, outbreak that began in China constitutes an international health emergency, on January 30, 2020 in Geneva. - The UN health agency declared an international emergency over the deadly coronavirus from China -- a rarely used designation that could lead to improved international co-ordination in tackling the disease. | FABRICE COFFRINI/AFP via Getty Images
Contents
Introduction
Enveloped, single-stranded, positive-strand RNA viruses classified within the Nidovirales order.
7 human coronaviruses (as of 31.01.2020):
Human coronavirus 229E (HCoC-229E)
Human coronavirus OC43 (HCoV-OC43)
SARS-CoV
Human coronavirus NL63 (HCoV-NL63, New Haven coronavirus)
Human coronavirus HKU1
Middle East respiratory coronavirus (MERS-CoV)
Wuhan coronavirus (2019-nCoV)
History
The name “coronavirus,” coined in 1968, is derived from the “corona”-like or crown-like morphology observed for these viruses in the electron microscope. In 1975, the Coronaviridae family was established by the International Committee on the Taxonomy of Viruses. Recently, at the 10th International Nidovirus Symposium in Colorado Springs, Colo., in June 2005, it was proposed that the Coronaviridae family be divided into two subfamilies, the coronaviruses and the toroviruses, the latter of which cause enteric diseases in cattle and possibly in humans. The Coronaviridae family, along with the Arteviridae and Roniviridae families, form the Nidovirales order. The Arteviridae family includes swine and equine pathogens, and the Roniviridae family is composed of invertebrate viruses.
Timeline of the key 2019-nCoV events | Gralinski, E. L., & Menachery, D. V. (2020). Return of the Coronavirus: 2019-nCoV. Viruses . https://doi.org/10.3390/v12020135
Microbiology
Anatomy:
Coronavirus virion. (A) Electron micrograph of MHV particles. (B) Schematic of virion. Viral particles contain an internal helical RNA-protein nucleocapsid surrounded by an envelope containing viral glycoproteins. Nucleocapsid (N) protein is a phosphoprotein that is complexed with genome RNA to form the nucleocapsid. Spike glycoprotein (S) forms the large glycosylated peplomers that are characteristic of coronaviruses. M, the transmembrane protein, is highly hydrophobic and spans the membrane three times. E, a membrane-spanning protein, is a minor component of the membrane. Some group II viruses express another glycoprotein, hemagglutinin-esterase (HE), which forms smaller spikes on virions. | Weiss, S. R., & Navas-Martin, S. (2005). Coronavirus Pathogenesis and the Emerging Pathogen Severe Acute Respiratory Syndrome Coronavirus. Microbiology and Molecular Biology Reviews, 69(4), 635 LP – 664. https://doi.org/10.1128/MMBR.69.4.635-664.2005
Replication:
Model of coronavirus replication. After receptor interaction and fusion of viral and plasma membranes, virus-specific RNA and proteins are synthesized, probably entirely in the cytoplasm. Expression of coronaviruses starts with translation of two polyproteins, pp1a and pp1ab, which undergo cotranslational proteolytic processing into the proteins that form the replicase complex. This complex is used to transcribe a 3′-coterminal set of nested subgenomic mRNAs, as well as genomic RNA, that have a common 5′ “leader” sequence derived from the 5′ end of the genome. Proteins are translated from the 5′ end of each mRNA. New virions are assembled by budding into intracellular membranes and released through vesicles by the cell secretory mechanisms. RER, rough endoplasmic reticulum; ER/GIC, endoplasmic reticulum/Golgi intermediate compartment. | Mani, H., & Jaffe, E. S. (2009). Hodgkin lymphoma: an update on its biology with new insights into classification. Clinical Lymphoma & Myeloma, 9(3), 206–216. https://doi.org/10.3816/CLM.2009.n.042
Epidemiology
Wuhan coronavirus (2019-nCoV):
SARS-CoV:
MERS:
Hui, D. S., Azhar, E. I., Kim, Y.-J., Memish, Z. A., Oh, M., & Zumla, A. (2018). Middle East respiratory syndrome coronavirus: risk factors and determinants of primary, household, and nosocomial transmission. The Lancet Infectious Diseases, 18(8), e217–e227. https://doi.org/10.1016/S1473-3099(18)30127-0
Transmission
Zoonosis: Animal to human transmission
Severe acute respiratory syndrome coronavirus (SARS-CoV) is a new coronavirus that emerged through recombination of bat SARS-related coronaviruses (SARSr-CoVs). The recombined virus infected civets and humans and adapted to these hosts before causing the SARS epidemic. Middle East respiratory syndrome coronavirus (MERS-CoV) likely spilled over from bats to dromedary camels at least 30 years ago and since then has been prevalent in dromedary camels. HCoV-229E and HCoV-NL63 usually cause mild infections in immunocompetent humans. Progenitors of these viruses have recently been found in African bats and the camelids are likely intermediate hosts of HCoV-229E. HCoV-OC43 and HKU1, both of which are also mostly harmless in humans, likely originated in rodents. Recently, swine acute diarrhoea syndrome (SADS) emerged in piglets. This disease is caused by a novel strain of Rhinolophus bat coronavirus HKU2, named SADS coronavirus (SADS-CoV); there is no evidence of infection in humans. Solid arrows indicate confirmed data. Broken arrows indicate potential interspecies transmission. Black arrows indicate infection in the intermediate animals, yellow arrows indicate a mild infection in humans, and red arrows indicate a severe infection in humans or animals. | Cui, J., Li, F., & Shi, Z.-L. (2019). Origin and evolution of pathogenic coronaviruses. Nature Reviews Microbiology, 17(3), 181–192. https://doi.org/10.1038/s41579-018-0118-9
