Evolution of SARS-COV-2

The COVID-19 pandemic is caused by a newly emerged coronavirus (SARS-CoV-2). The events associated with the spill-over have been the topic of unprecedented debate and speculation. Although no immediate viral ancestor of SARS-CoV-2 has been identified to date, nor an intermediate host, strong evidence suggests a zoonotic transmission from the wildlife, possibly associated with animal trade. Since the very beginning of the pandemic, the spread of the virus has been tracked nearly in real-time by genome surveillance programs and millions of SARS-CoV-2 genomes have been deposited in public databases. During these few years, the virus has been evolving as a result of different forces, such as mutation, recombination, and evasion of natural or vaccine-induced immune responses. Since the end of 2020, the emergence of new viral variants has dominated the epidemiology of COVID-19. The unpredictability of variant emergence urges for public health strategies to extend vaccination and maintain genomic surveillance.