13.1 Introduction

Learning Objectives

  • Describe the basic mechanism by which SARS-Cov-2 infects humans.
  • Identify some of the genes implicated in severe COVID-19 infection in humans.
  • Describe the various approaches for vaccine development against SARS-Cov-2.

Coronaviruses are a group of RNA viruses (i.e., their genetic material is RNA, rather than DNA) which cause diseases in mammals and birds, such as respiratory tract infections, which generally range from mild to lethal. Mild illnesses in humans include some cases of the common cold (which is also caused by other viruses, such as rhinoviruses), while more lethal varieties can cause SARS, MERS, and COVID-19. The most recent common ancestor of all coronaviruses is estimated to have existed as recently as 8000 BCE, although some models place the common ancestor as far back as 55 million years or more, implying long term co-evolution with bat and avian species.

The Coronavirus disease 2019 (COVID-19) is a contagious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 – Figure 13.1.1). The structural proteins of SARS-CoV-2 include membrane glycoprotein (M), envelope protein (E), nucleocapsid protein (N), and the spike protein (S).  The S-protein is the viral component that attaches to the host receptor via the ACE2 receptors, which is an enzyme on the surface of many cell types which generates small proteins by cleaving the large protein angiotensinogen, which that then go on to regulate functions in the cell. The first known infections from SARS-CoV-2 were discovered in Wuhan, China, somewhere between November – December 2019. The disease has since spread worldwide, leading to an ongoing pandemic. The original source of viral transmission to humans remains unclear, as does whether the virus became pathogenic before or after the spillover event.

SARS-CoV-2 infects people of all ages. However, evidence to date suggests that two groups of people are at a higher risk of getting severe COVID-19 disease. These are older people (people over 60 years old) and those with underlying medical conditions (such as cardiovascular disease, diabetes, chronic respiratory disease, and cancer). The risk of severe disease gradually increases with age starting from around 40 years.

Colorful image of SARS-CoV-2 showing blue spike proteins on a pink viral surface
Figure 13.1.1 Anatomy of SARS-CoV-2

Take a look at the video below, COVID-19 | Coronavirus: Epidemiology, Pathophysiology, Diagnostics, by Ninja Nerd (2020) on YouTube, which summarizes some important and interesting facts about coronaviruses from the Government of Canada (2020).

Media Attribution


Health Canada. (2020, March). COVID-19 | Coronavirus: Epidemiology, pathophysiology, diagnostics [Video file]. YouTube. https://www.youtube.com/watch?v=PWzbArPgo-o


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Open Genetics by Natasha Ramroop Singh, Thompson Rivers University is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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