Like all other viruses, the SARs-COV-2 virus is also programmed to mutate and hence, new variants are bound to emerge. "When a virus replicates or makes copies of itself, it sometimes changes a little bit, which is normal for a virus.

from Times of India https://timesofindia.indiatimes.com/life-style/health-fitness/health-news/coronavirus-what-are-the-covid-19-variants-present-in-india-along-with-omicron-and-their-symptoms/photostory/88688480.cms