They Are Large Family of Viruses first discovered in 1960. They are pleomorphic, single stranded RNA viruses. The name was derived from the crown like appearance produced by the club shaped projections that surrounds the viral envelope. They infect mostly the respiratory system causing upper respiratory infections (common colds) in mild cases or upper and lower respiratory infections in severe cases. Coronaviruses may also infect the gastrointestinal system on rare occasions.
There are currently seven known strains of Human Coronaviruses:
Four of them cause mild respiratory infections.
Three other strains are responsible for severe respiratory infections.