Coronavirus variants and mutations: the science explained

The discovery of two variants of coronavirus has triggered alarm.

Scientists are racing to find out whether these variants are more transmissible or could present challenges for the Covid vaccine.

All viruses naturally mutate, and Sars-CoV-2 is no exception, accumulating an estimated one or two changes a month.

Mutations are usually a chance event that will have little impact on the properties of a virus, says Dr Lucy van Dorp, an expert in the evolution of pathogens at University College London.

"The very vast majority of mutations which we observe in genomes of Sars-CoV-2 are there as passengers," she says.

"They don't change the behaviour of the virus, they are just carried along."