Coronaviruses are a group of mRNA viruses that may cause
diseases in mammals and birds. Human coronaviruses may cause mild to
moderate upper respiratory tract illnesses, and the first novel coronavirus
strain was discovered in the 1960s as being responsible for some cases of
the common cold in humans. In 2003, another novel coronavirus strain
was discovered to affect the upper and lower respiratory tracts, causing
severe acute respiratory syndrome (SARS) in humans and becoming
known as SARS-CoV.