Originally posted by Clinicians Brief on April 8, 2020, at 9:00 PM CST.

Coronaviruses: A Primer

Coronaviruses are enveloped viruses that typically cause respiratory and enteric disease in humans and animals,1 notably camels, bats, masked palm civets, mice, swine, cattle, horses, chickens, turkeys, dogs, and cats.2-4 Five coronaviruses are known to circulate in humans: four that cause the common cold, and Middle East respiratory syndrome coronavirus (MERS-CoV), which appeared in Saudi Arabia in 2012.1 A sixth coronavirus, severe acute respiratory syndrome coronavirus (SARS-CoV-1), emerged in 2002 from China and has not been seen since 2003. A seventh severe acute respiratory syndrome coronavirus (SARS-CoV-2), which causes coronavirus disease (COVID-19), emerged in Wuhan, China, in late 2019 with some exposures linked to the Huanan Seafood Wholesale Market; it is currently circulating at pandemic levels.5 Evidence suggests that bats serve as the ultimate reservoir for at least two of the human common-cold associated coronaviruses as well as for MERS-CoV, SARS-CoV-1, and SARS-CoV-2, which infect humans through intermediate animal hosts.1,6-8

Transmission

SARS-CoV-2 is transmitted person-to-person via droplets generated from talking, coughing, and sneezing that fall off after approximately six feet and can also be transmitted via fomites (ie, contaminated surfaces and objects).9,10 There is some evidence that aerosol transmission may be possible.11-13

SARS-CoV-2 can survive on some surfaces to a limited extent.11,13 One experimental study examined the survival of SARS-CoV-2 on plastic, stainless steel, copper, and cardboard.11 No viable virus was detected on copper after 4 hours or on cardboard after 24 hours, but virus was viable up to 72 hours on plastic and stainless steel. SARS-CoV-2 genetic material was also detected on environmental surfaces in Huanan Seafood Wholesale Market in China.6,9,14 Studies of other human coronaviruses have demonstrated survival of up to 9 days on certain surface types, with length of persistence correlated to inoculum dose and ambient temperatures.15