How did we get here? Short history of COVID-19 and other coronavirus-related epidemics.

The COVID-19 epidemic was not the first coronavirus epidemic of this century and represents one of the increasing number of zoonoses from wildlife to impact global health. SARS CoV-2, the virus causing the COVID-19 epidemic is distinct from, but closely resembles SARS CoV-1, which was responsible for the severe acute respiratory syndrome (SARS) outbreak in 2002. SARS CoV-1 and 2 share almost 80% of genetic sequences and use the same host cell receptor to initiate viral infection. However, SARS predominantly affected individuals in close contact with infected animals and health care workers. In contrast, CoV-2 exhibits robust person to person spread, most likely by means of asymptomatic carriers, which has resulted in greater spread of disease, overall morbidity and mortality, despite its lesser virulence. We review recent coronavirus-related epidemics and distinguish clinical and molecular features of CoV-2, the causative agent for COVID-19, and review the current status of vaccine trials.