SARS-CoV-2
What is SARS-CoV-2?
April 2020
Coronavirus disease 2019 (COVID-2019) is caused by a novel coronavirus known as Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and was identified as a pandemic by the World Health Organization (WHO) on March 11, 2020. As of April 12, 2020, more than 1.8 million people were confirmed to have been infected and tested positive for COVID-19, with over 114,000 deaths worldwide. This virus was first identified in the respiratory tract of patients with pneumonia in Wuhan, Hubei China, in December 2019 which was then indicated as a newly identified β-coronavirus (nCoV).
SAR-CoV2 is an enveloped, non-segmented, positive sense RNA virus that is included in the sarbecovirus, ortho corona virinae subfamily which is broadly distributed in humans and other mammals. Its diameter is about 65-125 nm, containing single strands of RNA and provided with crown-like spikes on the outer surface. SARS-CoV2 is a novel β-coronavirus after the previously identified SARS-CoV and MERS-CoV which led to pulmonary failure and potentially fatal respiratory tract infection and caused outbreaks mainly in Guandong, China and Saudi Arabia. In COVID-19 research, many studies have demonstrated that bats are suspected as the key reservoir of the viruses by finding as much as 96.2% identical genome sequencing of SARS-CoV-2 with bat CoV RaTG13.
Source: Indwiani Astuti, Ysrafil, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2): An overview of viral structure and host response[1]
Note: Each statement in this extract was referenced but the links have been removed. Please refer to the original article for details.
I chose the extract above because it is so succinct. The information is precise, reliable and based on research done by many others. The authors searched PubMed databases for Severe Acute Respiratory Syndrome Coronavirus-2, Middle East respiratory syndrome-related coronavirus and Severe Acute Respiratory Syndrome Coronavirus, retrieved and analyzed the full texts, and produced their paper as an easy-to-understand review. I am grateful for their efforts.
There are people who do not believe that a virus known as SARS-CoV-2 actually exists. Social media misinformation frequently asserts that the virus has never been isolated; that the genomic sequence is merely computer-generated; that the pandemic is a hoax. Denialists dismiss the reality of the global death-toll, and the collective beliefs could be called a covid denial syndrome. Countering misinformation is not my goal. It is time consuming and rarely productive. What I can do is present information I have learned during my own search for truth and hope that it is helpful to those who want to know.
Grant
July 2021
Contents
Virus and Disease Names
Viruses are named by the International Committee on Taxonomy of Viruses (ICTV).
In February 2003 an outbreak of a severe acute respiratory syndrome emerged in China and spread to 4 other countries[2]. This coronavirus was named Severe Acute Respiratory Syndrome (SARS) or SARS-CoV.
The novel (new) coronavirus which emerged in Wuhan, China in December 2019 was initially referred to as the 2019 novel coronavirus or 2019-nCoV. However, this new virus is genetically related to the coronavirus responsible for the SARS outbreak of 2003, so the ICTV officially named it severe acute respiratory syndrome coronavirus 2 which is abbreviated SARS-CoV-2[3]. For greater detail please refer to the article SARS-CoV-2/Taxonomy.
On 11 February 2020 the World Health Organisation named the disease caused by the new coronavirus COVID-19[3], a short form of the descriptor coronavirus disease 2019.
Growing the Virus
In January 2020 The Peter Doherty Institute for Infection and Immunity (Doherty Institute) in Melbourne (Australia) announced that scientists had successfully grown the 2019 novel coronavirus (COVID-19) from a patient sample. This is the first time the virus has been grown in cell culture outside of China.[4]
Survival of the Virus
In October 2020 researchers at CSIRO, Australia's national science agency, published results from a study on the effect of temperature on persistence of SARS-CoV-2 on common surfaces[5]. They found that SARS-CoV-2, the virus responsible for COVID-19, can survive for up to 28 days on common surfaces including banknotes, glass – such as that found on mobile phone screens - and stainless steel. They found that that SARS-CoV-2:
- survived longer at lower temperatures
- tended to survive longer on non-porous or smooth surfaces such as glass, stainless steel and vinyl, compared to porous complex surfaces such as cotton
- survived longer on paper banknotes than plastic banknotes
The research was undertaken at the Australian Centre for Disease Preparedness (ACDP)[6] in Geelong.
The CSIRO has been significantly involved in COVID-19 vaccine and antiviral research and a section on their website is very informative.[7].
Structure
What does SARS-CoV-2 look like?
Three images are reproduced below. The first is obviously a graphic design, a neatly symmetrical, spherical model created to illustrate the important features of the virus, the 'structural proteins'.
The second image is more realistic as it was through an electron microscope, but note that it has been 'colorized' so it is more engaging.
The third image illustrates the whole SARS-CoV-2 virion containing the viral RNA genome.
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Source: Centers for Disease Control and Prevention's Public Health Image Library, Public domain, via Wikimedia Commons
Image created by Alissa Eckert, MS; Dan Higgins, MAM
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This transmission electron microscope image shows SARS-CoV-2, the virus that causes COVID-19, isolated from a patient in the U.S. Virus particles are shown emerging from the surface of cells cultured in the lab. The spikes on the outer edge of the virus particles give coronaviruses their name, crown-like.
Image captured and colorized at NIAID's Rocky Mountain Laboratories (RML) in Hamilton, Montana. Credit: NIAID
Source: National Institute of Allergy and Infectious Diseases (NIAID), CC BY 2.0, via Wikimedia Commons
Source: SARS-CoV-2: vaccines in the pandemic era[8]
Transmission
The SARS-CoV-2 virus emerged in Wuhan, Hubei China, in December 2019. However, person-to-person transmission of the virus was not acknowledged until 24 January 2020. In Vietnam a confirmed case who had not travelled to China was a family member of a confirmed case who visited Wuhan; which suggested an instance of human to human transmission. In the Situation Report No 4 on 24 January 2020 the WHO stated:-
New epidemiological information reinforces the evidence that the 2019-nCoV can be transmitted from one individual to another. During previous outbreaks due to other coronavirus (Middle-East Respiratory Syndrome (MERS) and the Severe Acute Respiratory Syndrome (SARS)), human to human transmission occurred through droplets, contact and fomites, suggesting that the transmission mode of the 2019-nCoV can be similar.
Source: WHO Novel Coronavirus (2019-nCoV) SITUATION REPORT - 4 24 JANUARY 2020
The concept of social distancing at 1.5 to 2 metres, six feet, one crocodile or alligator, and other measures is based on the belief that a droplet containing the virus and expressed from a person by a cough, sneeze or outward breath would likely travel no more than about 2 metres before falling to the ground. It took the WHO about a year to acknowledge that the virus could spread as an aerosol:-
We know that the disease is caused by the SARS-CoV-2 virus, which spreads between people in several different ways.
The virus can spread from an infected person’s mouth or nose in small liquid particles when they cough, sneeze, speak, sing or breathe. These particles range from larger respiratory droplets to smaller aerosols.
Current evidence suggests that the virus spreads mainly between people who are in close contact with each other, typically within 1 metre (short-range). A person can be infected when aerosols or droplets containing the virus are inhaled or come directly into contact with the eyes, nose, or mouth.
The virus can also spread in poorly ventilated and/or crowded indoor settings, where people tend to spend longer periods of time. This is because aerosols remain suspended in the air or travel farther than 1 metre (long-range).
People may also become infected by touching surfaces that have been contaminated by the virus when touching their eyes, nose or mouth without cleaning their hands.
Source: WHO Coronavirus disease (COVID-19): How is it transmitted? (updated on 30 April 2021)
Infection
How does SARS-CoV-2 infect human cells?
Using the spike-like protein on its surface, the SARS-CoV-2 virus binds to ACE2 – like a key being inserted into a lock – prior to entry and infection of cells. Hence, ACE2 acts as a cellular doorway – a receptor – for the virus that causes COVID-19.
Source: The Conversation, What is the ACE2 receptor, how is it connected to coronavirus and why might it be key to treating COVID-19? 14 May 2020
A diagram illustrating this process is shown below:-
SARS–CoV-2 infects host cells through the specific binding of spike glycoprotein on the viral envelope and the angiotensin-converting enzyme 2 (ACE2) receptor on the host cell’s surface.
Source: Chen, S.-J.; Wang, S.-C.; Chen, Y.-C. Novel Antiviral Strategies in the Treatment of COVID-19: A Review. Microorganisms 2020, 8, 1259. https://doi.org/10.3390/microorganisms8091259, via Wikimedia Commons
Image created by Shiu-Jau Chen, Shao-Cheng Wang, and Yuan-Chuan Chen
See also Nature Structure of the SARS-CoV-2 spike receptor-binding domain bound to the ACE2 receptor 30 March 2020[9] which describes the processes in more detail.
COVID-19 and Angiotensin-converting enzyme 2 (ACE2)
When infection with SARS-CoV-2 occurs, the spike proteins bind to ACE2 receptors and the disease COVID-19 may progress beyond a mild case. The article ACE2 provides an introduction and three linked articles provide more detail:-
- ACE2 and COVID-19
- ACE2 and Vaccines, and
- ACE2 and early treatment
References
- ↑ Indwiani Astuti, Ysrafil, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2): An overview of viral structure and host response Diabetes & Metabolic Syndrome: Clinical Research & Reviews, Volume 14, Issue 4, 2020, Pages 407-412, ISSN 1871-4021, https://doi.org/10.1016/j.dsx.2020.04.020
(https://www.sciencedirect.com/science/article/pii/S1871402120300849)
From the Abstract: "We searched PubMed databases for Severe Acute Respiratory Syndrome Coronavirus-2, Middle East respiratory syndrome-related coronavirus and Severe Acute Respiratory Syndrome Coronavirus. Full texts were retrieved, analyzed and developed into an easy-to-understand review." - ↑ World Health Organisation Severe Acute Respiratory Syndrome (SARS)
- ↑ 3.0 3.1 World Health Organization Naming the coronavirus disease (COVID-19) and the virus that causes it
The guidelines for naming a disease excludes names that refer to a geographical location, an animal, or an individual or group of people. The name must also be pronounceable and related to the disease. So the new disease could not be officially called the China Virus or the Wuhan Flu, terms used frequently by US President Trump during his term of office. - ↑ Doherty Institute scientists first to grow and share 2019 novel coronavirus 20 January 2020
- ↑ CSIRO (Australia) CSIRO scientists publish new research on SARS-COV-2 virus ‘survivability’ News Release, 12 October 2020
Note: Results from the study The effect of temperature on persistence of SARS-CoV-2 on common surfaces was published in Virology Journal. - ↑ CSIRO Inside the Australian Centre for Disease Prepardeness
The Australian Centre for Disease Preparedness (ACDP) is a high-containment facility designed to allow research into the most dangerous infectious agents in the world. - ↑ CSIRO COVID-19 vaccine and antiviral research
- ↑ Li, DD., Li, QH. SARS-CoV-2: vaccines in the pandemic era. Military Med Res 8, 1 (2021). https://doi.org/10.1186/s40779-020-00296-y
- ↑ 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
