The Origins of the Emerging Novel Coronavirus
Laila Khorasani
April 07 2020
April 07 2020
Ever since the emergence of a rapidly spreading pneumonia in Wuhan, China, a significant effort has been put into researching the origins and transmission of the disease now known as COVID-19. While the virus behind this, SARS-CoV-2, is the seventh of the coronavirus family to infect humans, it is one of very few to cause severe symptoms and infect thousands in a short period of time. Recently, the World Health Organization (WHO) officially declared the current situation a pandemic as the disease has reached worldwide proportions. Because of the disastrous public health implications of a highly contagious respiratory illness, it becomes imperative to understand the biological origins and transmission mechanisms of this novel coronavirus.
In order to attack and infiltrate healthy host cells, SARS-CoV-2 takes advantage of spike proteins on its surface to specifically bind to human receptor ACE2 (like how a key fits into a lock). ACE2 is found on two distinct cell types within the human airway and lungs. This explains why individuals infected with SARS-CoV-2 may experience severe respiratory symptoms, such as shortness of breath, which could lead to pneumonia and body-wide infection in critical cases. Since the virus specifically targets the lungs, it becomes easily transmittable through sneezing and coughing. Spike proteins have been characterized across many different members of the coronavirus family. However, there is one region of the spike proteins in SARS-CoV-2 that is unique, thereby allowing it to attack human respiratory cells (through binding to ACE2 receptors). This region is called the receptor-binding domain (RBD), and it has been actively studied since its discovery. Because this one region allows the virus to bind to ACE2 receptors, this means that the disease can theoretically infect any organism that has ACE2 receptors similar to those of humans.
In order to attack and infiltrate healthy host cells, SARS-CoV-2 takes advantage of spike proteins on its surface to specifically bind to human receptor ACE2 (like how a key fits into a lock). ACE2 is found on two distinct cell types within the human airway and lungs. This explains why individuals infected with SARS-CoV-2 may experience severe respiratory symptoms, such as shortness of breath, which could lead to pneumonia and body-wide infection in critical cases. Since the virus specifically targets the lungs, it becomes easily transmittable through sneezing and coughing. Spike proteins have been characterized across many different members of the coronavirus family. However, there is one region of the spike proteins in SARS-CoV-2 that is unique, thereby allowing it to attack human respiratory cells (through binding to ACE2 receptors). This region is called the receptor-binding domain (RBD), and it has been actively studied since its discovery. Because this one region allows the virus to bind to ACE2 receptors, this means that the disease can theoretically infect any organism that has ACE2 receptors similar to those of humans.
Bats are one of the organisms that are suspected to have been the original host for the virus that evolved to be SARS-COV-2.
While the exact origins of the virus remain unknown, preliminary evidence indicates that it likely originated in an animal host and mutated to infect humans either before, during, or after a zoonotic transfer. Given a strong history of similar SARS-CoV diseases originating in bats, they likely represent one such animal host in this current coronavirus pandemic. Genomic analysis of a suspected Rhinolophus affinis bat coronavirus (abbreviated as RaTG13) shows that 96% of their genome is identical to that of SARS-CoV-2. However, stark differences between these viruses exist at a critical point in the genome: the spike-proteins. While this isn’t entirely disqualifying, it indicates that it’s unlikely that the RaTG13 is a direct ancestor of SARS-CoV-2. Recent reports have also implicated pangolins as a potential host carrier for a genetically similar coronavirus. Pangolin coronaviruses are less similar to SARS-CoV-2 overall compared to RaTG13, but they do share the critical RBD region of the spike proteins. Even so, there is still uncertainty surrounding the exact molecular origins for this novel coronavirus, and far more work needs to be done in order to better identify its natural history. While the specific scientific mannerisms of the virus may not seem of utmost importance in this global crisis, they may provide insights into SARS-CoV-2 transmission, origin possibilities for future pandemics, and strategies to decrease transmission.
Featured Image Source: Pixabay
RELATED ARTICLES
|
Vertical Divider
|
Vertical Divider
|
Vertical Divider
|
