関連性A novel coronavirus has been identified as the causative agent of SARS (Severe Acute Respiratory Syndrome). Coronaviruses are a major cause of upper respiratory diseases in humans. The genomes of these viruses are positive stranded RNA approximately 27 to 31kb in length. SARS infection can be mediated by the binding of the viral spike protein, a glycosylated 139 kDa protein and the major surface antigen of the virus, to the angiotensin converting enzyme 2 (ACE2) on target cells. This binding can be blocked by a soluble form of ACE2.