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This chapter introduces the severe life-threatening human coronaviruses and their emergence including the Wuhan outbreak, the initial transmission of SARS-CoV-2, its viral classification and genomic architecture, as well as the epidemiology and pathophysiology of COVID-19. In the space of just eight months, this new coronavirus has literally dominated our minds and our lives – causing fear, a world-wide pandemic, and economic disaster.

While human coronaviruses (CoV) were first identified in the mid 1960s, the emergence of severe life-threatening human coronavirus-related diseases was not detected until the 21st century with the advent of the Severe Acute Respiratory Syndrome coronavirus (SARS-CoV) and the Middle East Respiratory Syndrome coronavirus (MERS-CoV). Coronaviruses (CoVs) are a large family of zoonotic single-stranded RNA viruses that occur in numerous wild and domesticated animal species, are known to occasionally cross species barriers, and may cause illness in humans ranging from the common cold to more severe diseases such as SARS and MERS. SARS-CoV and MERS-CoV likely originated in bats and then infected other mammalian hosts — the Himalayan palm civet for SARS-CoV, and the dromedary camel for MERS-CoV — before being transmitted to humans.

When an outbreak of a disease similar to SARS emerged in Wuhan, China, in December 2019, researchers suspected that a new coronavirus had spread to humans. Most, but not all, of the Wuhan cases of ’pneumonia of unknown origin’ identified were linked to a single live-animal market in the city. Researchers in China immediately began to isolate and sequence the virus. When SARS-CoV had emerged in 2002, months passed before a full virus genome sequence became available. This time it was possible to decipher the virus’s RNA code within weeks of the appearance of the first case. Although the dynamics of SARS-Cov-2 are currently unknown, it is likely that it also originated in some species of bat. Its genetic architecture is very similar to BatCoV RaTG13 as well as SARS-CoV. Thus. it was named SARS-CoV-2 by the International Committee on Taxonomy of Viruses (ICTV) and ’novel coronavirus 2019’ or ’COVID-19’ by the World Health Organization (WHO).