Among the seven human CoVs, two α-coronaviruses (HCoV-229E and HCoV-NL63) and two β-coronaviruses (HCoV-OC43 and HCoV-HKU1) were thought to cause only mild self-limiting upper respiratory disease, such as common cold in immunocompetent hosts, except for a few cases of severe infections in infants, children and seniors [12,13]; the other three CoVs could cause fatal respiratory diseases.