Four Omicron sub-variants are in circulation across the world, WHO warns

Four sub-variants of the Omicron Covid strain are currently in circulation across the globe, the World Health Organisation (WHO) has said.

The first version of the Omicron variant was identified towards the end of last year and was named B.1.1.529,

This then developed into BA.1, which became highly transmissible and spread to 171 countries across the world.