Covid-19 variants explained, and how the virus mutates in the human body

Originally called the Indian variant or B.1.671.2, the Delta variant surged through India, causing a huge spike in infections and deaths earlier this year. — AP

All viruses mutate all the time, especially when they are replicating in a host body.

Therefore, the more people get infected by a certain virus, the more opportunities the virus has to mutate.