Officials are keeping a close watch on a new descendant of the Delta variant of Covid that is causing a growing number of infections.

Delta is the UK's dominant variant, but latest official data suggests 6% of Covid cases that have been genetically sequenced are of a new type.

AY.4.2, which some are calling "Delta Plus", contains mutations that might give the virus survival advantages.

Tests are under way to understand how much of a threat it may pose.

Experts say it is unlikely to take off in a big way or escape current vaccines.

It is not yet considered a variant of concern, or a variant under investigation - the categories assigned to variants and the level of risk associated with them.

Original Delta was classified as a variant of concern in the UK in May 2021 after overtaking the Alpha variant to become the dominant type of Covid in circulation.