1: Introduction

Coronaviruses are a family of enveloped positive-sense single-stranded ribonucleic acid (RNA) viruses that were first discovered during the 1960s. Compared to other RNA viruses, such as the Human Immunodeficiency Virus Type 1 that is between 9,200 to 9,600 nucleotides, coronaviruses have larger genome sizes, ranging from 27 to 34 kilobases (German Advisory Committee Blood, 2016). The name coronavirus is derived from the Latin word ‘corona’, which means ‘crown’ or ‘halo’. It has been given this name due to its outer appearance (Valencia, 2020) (see Image 1.1).

There are several different types of coronaviruses that are known to cause disease in humans, including Alphacoronaviruses and Betacoronaviruses. It is widely accepted, particularly among those who study coronaviruses, that Alphacoronaviruses and Betacoronaviruses originated from the bat species Rousettus leschenaultii. Not all types of coronaviruses, however, can cause serious illness or death. For example, strains 229E and NL63 of Alphacoronaviruses and strains OC43 and NKU1 of Betacoronaviruses often cause mild flu-like symptoms in humans. However, the Middle East respiratory syndrome (MERS-CoV), severe acute respiratory syndrome coronavirus (SARS-CoV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) commonly cause severe respiratory illnesses in humans (Valencia, 2020).