Transient acquisition of cross-species infectivity during the evolution of SARS-CoV-2.

Abstract

Summary The emergence and global spread of SARS-CoV-2 variants has caused global concerns about increased virulence and decreased efficacy of medical countermeasures. Herein, we demonstrate that the newly emerged 501Y.V2 variant (also called the beta variant) is capable of infecting standard laboratory mice after intranasal instillation, unlike the earlier isolates. However, the infectivity in mice demonstrated in the laboratory may not occur in nature; indeed, there is no evidence of natural transmission of 501Y.V2 in mice to date. Most interestingly, the 501Y.V2 variant was quickly replaced by another variant—the delta variant—in the human population. Our results indicate that circulating SARS-CoV-2 has been evolving rapidly and that transient acquisition of cross-species infectivity in animals may occur. This phenomenon creates new challenges as well as opportunities in studying SARS-CoV-2 circulation and evolution.