Furthermore, the close relatedness between W1V1 and SARS-CoV was confirmed by neutralization effect of convalescent SARS patient sera on W1V1. The isolation of a bat SL-CoV genetically closely resembling SARS-CoV and having a functional S protein capable of using the same ACE2 receptor of SARS-CoV provided robust and conclusive evidence for the bat origin of SARS-CoV.