Context

The novel coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 virus) has affected more than half-a-million people across the globe. As the numbers have been increasing by the hour, it is important to understand the origins of SARS-CoV-2 virus in order to deconstruct it and find a cure for COVID-19.

About

• SARS coronavirus (SARS-CoV) – virus was identified in 2003. SARS-CoV is thought to be an animal virus from an animal reservoir, perhaps bats, that spread to other animals (civet cats).
• It first infected humans in the Guangdong province of southern China in 2002.
• SARS is caused by a strain of coronavirus, the same family of viruses that causes the common cold.
• Transmission of SARS-CoV is primarily from person to person. Most respiratory illnesses, including SARS, spread through droplets that enter the air when someone with the disease coughs, sneezes or talks.

What the study says?

• A research published in the journal Pathogen suggested that the virus likely jumped to humans from Pangolins, one of the most trafficked animals in the world. 
  • Pangolins are illegally sold in the wildlife markets of China such as the Huanan market in Wuhan city.
  • There are eight species of pangolins:
    • Four are found is Asia—Chinese, Sunda, Indian, and Philippine pangolins—and they're listed by the IUCN as critically endangered
    • The four African species—the ground pangolin, giant pangolin, white-bellied, and black-bellied—are listed as vulnerable
  • Most initial positive COVID-19 cases were linked to Wuhan, which was the epicentre of the outbreak till a few weeks ago.
  • According to a research paper published in Nature Medicine, the original source of the virus was bats, and pangolins might have acted as intermediaries.
  • The mutation and natural selection might have taken place either inside pangolins or in humans after transfer from pangolins.
  • SARS-CoV-2 could be a recombinant organism formed by the genetic mix-up of two different viruses infecting the same carrier animal.
  • This is because none of the known coronaviruses seemed to be the parent virus which got mutated to give birth to SARS-CoV-2.
  • Such mechanisms have also been put forth for the origin of other coronaviruses like the SARS-CoV virus.
  • In the initial days of the outbreak, it was speculated that SARS-CoV-2 was deliberately genetically engineered. However, there is no evidence to support the claim so far.
  • Another paper published in Nature stated that the mutation was different from what was predicted from previously known genetic systems.

 How RBD facilitates the virus?

• SARS-CoV-2 has spike proteins which contain a receptor-binding domain (RBD).
• The RBD facilitates the virus’ entry into target cells by binding with the angiotensin-converting enzyme-2 (ACE-2) found in heart, lungs, kidneys and the gastrointestinal tract.
• RBD of the SARS-CoV-2 could be a mutated version of RBD of the RaTG13 virus, found in a species of bat of scientific name Rhinolophus affinis.
• The species were found in the Yunan province of China. In fact, the two viruses share an overall genetic similarity of 96 percent.
• Another virus with greater genetic similarity to SARS-CoV-2’s RBD is found in Malayan pangolins.
• The mutation increased the RBD’s bonding affinity with the ACE-2 of target cells in humans, ferrets and Malayan Pangolins.
• This bonding is stronger in SARS-CoV-2 virus than it was in SARS-CoV virus, which caused the SARS [Severe Acute Respiratory Syndrome] epidemic in 2002-2003 across 29 countries.
• The stronger bonding affinity partly explains CoVID-19’s faster spread.
• The research is on, and sooner or later, the world will hopefully know the truth about the virus.