Covid variants: How many Covid-19 variants are there?
There are many thousands of different versions, or variants, of Covid circulating including the Kent variant, Brazil variant and South African variant.
The Kent variant is now the most commonly found strain in the UK and it's more easily spread than the first variant, which arrived in Spring 2020.
Scientists are looking at tweaking the coronavirus vaccines to make sure they continue to protect people.
But where are these variants coming from? What are these new variants? And why do viruses mutate in the first place?
Health correspondent Laura Foster and virologist Dr Cindy Duke explain.
Video by Laura Foster