Matter Magazine: The Science Behind the Virus:
By Lina Huang
COVID-19 has currently clocked 39.8 million cases and 1.11 million deaths. Still ongoing, the pandemic is one of the sources of too much pain and hurt. The cause of the COVID-19 pandemic is a single virus, denominated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
SARS-CoV-2 belongs to a class of viruses known as coronaviruses for the crown-like shape of their outer spikes. This class of viruses are thought to cause a third of all common colds in humans due to shared properties that increase infection, mutation rate, and replication. The SARS-CoV, another coronavirus, caused the 2002-2003 SARS epidemic in China.
Like other viruses, SARS-CoV-2 is enveloped in a lipid membrane stolen from the infected cell. Inside the virus lies the genetic material, which is single-stranded ribonucleic acid (RNA) for all coronaviruses, including SARS-CoV-2. Once the virus infects a cell, the injected viral RNA is then used to make mRNA, which may be translated by ribosomes into protein.
The outer membrane of the virus contains a marker, S-glycoprotein, which is used to bind to the angiotensin-converting enzyme 2 (ACE2) on human cells, allowing the virus to infect the cell. The ACE2 marker is abundant in the lower neck and lung area of the body, accounting for the spread of SARS-CoV-2 through coughing and breathing. However, the marker is located everywhere throughout the body on arteries and veins, and physicians have seen COVID-19 damage the kidney, liver and spleen.
The mechanisms by which SARS-CoV-2 uses ACE2 to infect cells is still not fully elucidated, but it appears that the human cell participates in allowing the virus in. After attachment of the virus, the human cell exposes amino acids (the constituents of proteins) which open the human cell’s membrane so that the virus membrane can merge with it. In this way, the two membranes combine, allowing the virus to release its genetic material inside.
Furthermore, the genetic material–the RNA–of SARS-CoV-2 is concerning because of its high mutation rate. The enzyme RNA-dependent RNA polymerase is provided by the virus, and the enzyme’s tendency to mismatch base pairs accounts for this mutation rate. More alarmingly, SARS-CoV-2 is able to recombine its genetic material with other coronaviruses, giving rise to different versions of the virus which may be more devastating.
The structure of SARS-CoV-2 is particularly of interest for scientists because it allows for COVID-19 testing. Molecular tests diagnose COVID-19 through detection of viral RNA. The sequencing of COVID-19 RNA has allowed scientists to identify those sequences characteristics of COVID-19, which the test is based on.
Lastly, understanding the biology of the SARS-CoV-2 virus provides important knowledge for the development of vaccines. Currently, there is no effective vaccine approved for COVID-19, and measures to confront the virus, including ventilator use and antibiotic and antifungal treatment, are currently targeting the symptoms instead of the virus itself. For the most part, vaccines rely on stimulating the human immune system to recognize features of SARS-CoV-2. To develop vaccines that can do that, we first must understand these characteristics of the virus that causes COVID-19.