Each time you see a branching on the left graph, that is a mutation leading to a slightly different variant of the virus.
All viruses mutate slightly from time to time and experts in the field indicate that the COV-19 may mutate slightly approximately 2 times per month. These mutations does not necessary mean that different forms of the virus is formed (think each generation of a human where DNA is a mix of both parents…while the child is genetically different from both parents (contains DNA sequences of both), the child is not a new variant of the human population). The same applies to the flu which mutates significantly quicker than COVID-19…and variants can take a season or more to change significantly, even though there has been many generations of the flu virus infecting many of the world’s population each year.
If viruses changed significantly between generations, the potential benefit of using vaccinations would be limited, particularly temporally (maybe weeks or months rather than a flu season).
Experts also indicate that there are only two strains of the COV-19 infecting the world’s population.
The WHO has also indicated that "World Health Organization insists that “there is no evidence that the virus has been changing”
This article presents information on the two stains which are currently rampant in the world… https://www.newscientist.com/article/2236544-coronavirus-are-there-two-strains-and-is-one-more-deadly/#ixzz6HZmNE3cZ"
More information can also be found on the WHO website in relation to the virus and whether slight mutations has resulted in significant change to the virus. The WHO website on the COVID-19 can be found here:
There has been some doomsday type media reports about (potential for) mutation of COVID-19. These reports add to the panic and concern of individuals. There have also been viral posts circulating which are based on unfounded information.