Coronavirus
First Published: 29 March 2020
Last Updated: 9 November 2020
The novel coronavirus, SARS-CoV-2, which stands for "severe acute respiratory syndrome coronavirus 2", is the virus that causes the disease COVID-19.1 The spread of COVID-19, which was first detected in Wuhan, China, posed an emergency of international concerns, and cases have been reported in more than 200 countries/regions that resulted in health, lives, and economic losses.2
Coronaviruses (also known as CoVs) are a family of viruses (such as SARS - severe acute respiratory syndrome and MERS - Middle East respiratory syndrome) that cause respiratory and intestinal illnesses in humans and animals.3
COVID-19 is a disease caused by a new strain of coronavirus. 'CO' stands for corona, 'VI' for virus, and 'D' for disease. Formerly, this disease was referred to as '2019 novel coronavirus' or '2019-nCoV.'
SARS-CoV-2 is primarily transmitted between people through respiratory (droplet and aerosol) and contact routes. Transmission risk is highest where people are in close proximity (within 2 metres). Airborne transmission can occur in health and care settings in which procedures or support treatments that generate aerosols are performed. Airborne transmission may also occur in poorly ventilated indoor spaces, particularly if individuals are in the same room together for an extended period of time.4
The World Health Organization (WHO) states that it takes 5 - 6 days on average from when someone is infected with the virus for symptoms to show, however it can take up to 14 days.
COVID-19 affects different people in different ways. Most infected people will develop mild to moderate illness and recover without hospitalization. It is advised to seek medical attention if an individual has serious symptoms such as difficulty breathing or shortness of breath, chest pain or pressure and loss of speech or movement.5
SARS-CoV-2 are enveloped and spherical viruses that have a diameter of around 80 and 120 nanometers (nm) in size (around 1,000 times smaller than the width of a human hair).
The RNA genome of coronaviruses is the longest among all RNA viruses, comprised of six to ten open reading frames (ORFs) that are responsible for encoding both the replicase and structural proteins for the virus. Each of the components of the viral genome is packaged into a helical nucleocapsid that is surrounded by a lipid bilayer.
The viral envelope of coronaviruses is typically made up of three proteins that include the membrane protein (M), the envelope protein (E), and the spike protein (S).6
The surface of the virus (one of the key biological characteristics of SARS-CoV-2), is covered with spike (S) proteins that enable the virus to enter and infect human cells.
As compared to the (M) and (E) proteins that are primarily involved in virus assembly, the S protein plays a crucial role in penetrating host cells and initiating infection. The presence of S proteins on the coronaviruses is what gives rise to the spike-shaped protrusions found on their surface. The spikes on the surface of coronaviruses give this virus family its name — corona, which is Latin for "crown," and most any coronavirus will have a crown-like appearance.
Spike (S) protein is the reason why viruses like SARS-CoV-2 are able to interact with cells of potential hosts such as animals and humans to cause infection.
Coronavirus uses its spike (S) protein to mediate membrane fusion and virus entry.7 As a result, the S protein represents an ideal target for vaccine and COVID-19 immunotherapies.
A stalk with three flexible hinges
The Spike (S) protein has a long, slender stalk and is connected to the viral surface by three hinges, making the (S) protein highly flexible. The flexibility of these hinges may explain how multiple spikes act in concert to engage onto the flat surface of a host cell.8
Glycan shield
The Spike (S) protein has a characteristically thick N-glycan coating. This glycan shield is a sugary barrier, creating the perfect camouflage that helps the viral SARS-CoV-2 to evade the body's immune system. 9
One of the leading coronavirus vaccine candidates has proven to be 90 per cent effective, marking a major breakthrough in the global race to stop the disease.
The first 'milestone' has been described as a "great day for science and humanity" by its developers, Pfizer and BioNTech. The preliminary results from a massive clinical trial suggest 9 out of 10 people who get their jab are protected from coronavirus by their vaccine.
This latest breakthrough is welcome and positive news, boosting confidence for the continued efforts within the medical and science community.
References
1 Lan, J., Ge, J., Yu, J. et al. Structure of the SARS-CoV-2 spike receptor-binding domain bound to the ACE2 receptor. Nature 581, 215-220 (2020). https://doi.org/10.1038/s41586-020-2180-5
2 Coronavirus Disease 2019 (COVID-19) Pandemic and Economic Impact. Tauseef Ahmad, Haroon, Mukhtiar Baig, and Jin Hui https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7306969/
3 Cui J, Li F, Shi ZL. Origin and evolution of pathogenic coronaviruses. Nature Reviews Microbiology. 2019 Mar;17(3):181-192. DOI: 10.1038/s41579-018-0118-9. https://europepmc.org/article/MED/30531947
4 Guidance: COVID-19: epidemiology, virology and clinical features. Updated 9 November 2020. https://www.gov.uk/government/publications/wuhan-novel-coronavirus-background-information/wuhan-novel-coronavirus-epidemiology-virology-and-clinical-features
5 Coronavirus: Health Topics. World Health Organization https://www.who.int/health-topics/coronavirus
6 What are Spike Proteins? B. Cuffari, M.Sc., Reviewed E. Henderson, B.Sc. https://www.news-medical.net/health/What-are-Spike-Proteins
7 Ou, X., Liu, Y., Lei, X. et al. Characterization of spike glycoprotein of SARS-CoV-2 on virus entry and its immune cross-reactivity with SARS-CoV. Nat Commun 11, 1620 (2020). https://doi.org/10.1038/s41467-020-15562-9
8 In situ structural analysis of SARS-CoV-2 spike reveals flexibility mediated by three hinges. Beata Turonova, Mateusz Sikora, Christoph Schurmann, Wim J. H. Hagen, Sonja Welsch, Florian E. C. Blanc, Soren von Bulow, Michael Gecht, Katrin Bagola, Cindy Horner, Ger van Zandbergen, Jonathan Landry, Nayara Trevisan Doimo de Azevedo, Shyamal Mosalaganti, Andre Schwarz, Roberto Covino, Michael D. Muhlebach, Gerhard Hummer, Jacomine Krijnse Locker, Martin Beck. https://science.sciencemag.org/content/370/6513/203
9 Beyond Shielding: The Roles of Glycans in the SARS-CoV-2 Spike Protein. Lorenzo Casalino, Zied Gaieb, Jory A. Goldsmith, Christy K. Hjorth, Abigail C. Dommer, Aoife M. Harbison, Carl A. Fogarty, Emilia P. Barros, Bryn C. Taylor, Jason S. McLellan, Elisa Fadda, and Rommie E. Amaro. ACS Central Science 2020 6 (10), 1722-1734. DOI: 10.1021/acscentsci.0c01056
10 Covid vaccine: First 'milestone' vaccine offers 90% protection. BBC Health News. https://www.bbc.co.uk/news/health-54873105
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