Pathogens
CoVs are a large family of single-stranded RNA viruses that infect humans primarily through droplets and fomites. Before December 2019, there were 6 known human CoVs, including the alpha-CoVs, HCoV-NL63 and HCoV-229E, and the beta-CoVs, HCoV-OC43, HCoV-HKU1, severe acute respiratory syndrome-COV (SARS-CoV) and middle east respiratory syndrome (MERS-CoV).2 The recently identified COVID-19 is a beta-CoV that infects both humans and animals. All 3 of these novel viruses (SARS-CoV, MERS-CoV and COVID-19) originate from zoonotic transmission. Bats may have served as the source of SARS-CoV and COVID-19 based on sequence similarity with bat CoVs. Camels are suspected to have been the zoonotic host for transmission of MERS-CoV.
The SARS-CoV outbreak spanned from 2002 to 2003 infecting 8,098, causing 774 deaths resulting in a 5-10% mortality and a 43% mortality in the elderly.3 , 4 The MERS-CoV outbreak was first reported in Saudi Arabia in 2012.4 It then spread to Europe, Asia, Africa and North America and infected 2,494 people, causing 858 death.5 The MERS-CoV caused severe pneumonia with an intensive care unit (ICU) admission rate of 40-50% and an in-hospital ICU death rate of 75%.6 , 7 In December 2019, the city of Wuhan in Hubei Provence, China, reported a small outbreak of a novel coronavirus, COVID-19. The fatality rate is highest in adults ≥85 years old (10-27%), followed by 65-84 years (3-11%) with 50% of ICU admission among persons ≥65 years. The World Health Organization declared COVID-19 as a pandemic on March 11, 2020.