Coronavirus explainer: How the crown-wearing viruses infected the human race

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Coronaviruses are a diverse family of viruses, which can infect a large range of hosts. Due to their spike-like projections on their surface, they can resemble a crown. In Latin, corona means crown – hence their name.

There are human coronaviruses that cause mild respiratory illnesses, such as the common cold.

Researchers from Penn State University College of Medicine, USA, stated human coronavirus “have long been considered inconsequential pathogens”.

However, three have emerged in the 21st century that have caused alarming disease and death:

  • SARS-CoV (severe acute respiratory syndrome coronavirus)
  • MERS-CoV (Middle East respiratory syndrome coronavirus)
  • SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2)

What do they have in common?

All coronaviruses “are large, enveloped, positive strand RNA viruses” that can be divided into four groups:

  • Alpha
  • Beta
  • Delta
  • Gamma

“Alpha and beta coronaviruses are known to infect humans,” stated the researchers.

The surface spike protein (S) glycoprotein is “critical” for binding to host cell receptors.

SARS-CoV (beta)

“Cases of severe atypical pneumonia were described in Guangdong Province, China” in 2002.

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International travel enabled SARS-CoV to spread to “more than two dozen countries”.

Early cases were traced back to “live game markets”, resulting in zoonotic transmission (from animal to humans) being hugely suspected.

“Consensus emerged that bats were the natural hosts,” they reported, meaning coronaviruses could “jump the species barrier”.

The predominant human receptor for the coronavirus surface spike protein (S) glycoprotein is angiotensin-converting enzyme 2 (ACE2) – found primarily in the lower respiratory tract.

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Public health measures brought the SARS-CoV pandemic to an end, with 774 people having lost their lives.

MERS-CoV (beta)

In 2012, MERS-CoV emerged. Characterised by “sporadic zoonotic transmission and limited chains of human spread”.

According to the World Health Organisation (WHO), as of November 2019, MERS-CoV has caused 858 deaths, mostly in Saudi Arabia.

Those with MERS-CoV have “gastrointestinal symptoms” explained by the MERS-CoV (S) glycoprotein binding to dipeptidyl peptidase 4 (DPP4) – also present in the lower airways, as well as the gastrointestinal tract.

These two noteworthy viruses illustrated zoonotic coronaviruses posed a “threat” to humans.

In response, the WHO began research in the development of countermeasures against coronaviruses in 2017.

SARS-CoV-2 (beta)

As with SARS-CoV, this virus that swept the globe by storm in 2020 also uses ACE2 as a receptor to bind with.

Moreover, SARS-CoV-2 is also though to have originated in bats, stated Healthline.

The thing that sets SARS-CoV-2 apart from the other coronaviruses is the impact it’s had on the world.

As “80 percent of people” infected with SARS-CoV-2 have a mild illness, it’s highly transmissible when people carry on with their daily lives.

SARS-CoV, on the other hand, led to more “severe” cases and is considered more deadly upon infection.

As vaccine trials are underway to manage coronaviruses, and public health measures are in place, soon this pandemic may be put to an end.

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