Within the past month new novel coronavirus variants have appeared in the UK, in South Africa, and in Brazil. These variants are more robust than the original virus, able to infect more easily and spread more rapidly. Possibly they are also more deadly, more virulent, data does hint at the possibility, but conclusive scientific data one way or the other has yet to emerge. Possibly they are also more resistant to the current vaccines and to the human immune system, though again conclusive scientific data one way or the other is not yet available.
These variants are gradually replacing the original coronavirus. It is estimated that in the United States that 1/3 of infections will be from the UK variant by mid-year, whereas right now its representation among infected individuals is miniscule. This is precisely what beneficial mutations do, outcompete and replace other variants.