What are the India, Brazil, South Africa and UK variants?

A mutated version of coronavirus, first identified in India and now circulating in the UK too, has been classified as "of concern" by UK public health experts.

The world is carefully monitoring this and some other new genetic types of the pandemic virus that may be able to spread more easily, make people sicker, or overpower vaccines. 

Understanding new variants can help governments adjust vaccination programmes and keep the virus under control.

All viruses change as they make copies of themselves to survive and spread.

Most changes are inconsequential, and some can even harm the virus. But others can make the disease more infectious or threatening – and these mutations tend to dominate. 

If lots of its human hosts have gained immunity through infection or vaccination, a virus with mutations that can evade this protection will thrive. 

To work out whether a mutation is dangerous, scientists look for warning signs in the virus's genetic code, see how it behaves in a lab, and monitor its spread in people.