A coronavirus is one of many viruses that cause diseases in mammals and birds. In humans, coronaviruses cause respiratory tract infections that are typically mild, such as the common cold, though rarer forms such as SARS, MERS and COVID-19 can be lethal.
Symptoms vary in other species: in chickens, they cause an upper respiratory tract disease, while in cows and pigs, they cause diarrhea. There are currently no vaccines or antiviral drugs to prevent or treat human coronavirus infections.
The name coronavirus is derived from the Latin corona, meaning "crown" or "halo", which refers to the characteristic appearance of the virus particles: they have a fringe reminiscent of a crown or of a solar corona.
Coronaviruses were first discovered in the 1960s. The earliest ones discovered were infectious bronchitis virus in chickens and two viruses from the nasal cavities of human patients with the common cold that were subsequently named human coronavirus 229E and human coronavirus OC43. Other members of this family have since been identified, including SARS-CoV in 2003, HCoV NL63 in 2004, HKU1 in 2005, MERS-CoV in 2012, and SARS-CoV-2 (formerly known as 2019-nCoV) in 2019; most of these have been involved in severe respiratory tract infections.
Human to human transmission of coronaviruses is primarily thought to occur among close contacts via respiratory droplets generated by sneezing and coughing.
Coronaviruses are believed to cause a significant proportion of all common colds in adults and children. Coronaviruses cause colds with significant symptoms, such as fever and sore throat from swollen adenoids, primarily in the winter and early spring seasons. Coronaviruses can cause pneumonia – either direct viral pneumonia or secondary bacterial pneumonia – and may cause bronchitis – either direct viral bronchitis or secondary bacterial bronchitis. The much-publicized human coronavirus discovered in 2003, SARS-CoV, which causes severe acute respiratory syndrome (SARS), has unique pathogenesis because it causes both upper and lower respiratory tract infections. There are currently no vaccines or antiviral drugs to prevent or treat human coronavirus infections
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