A new Covid variant has been detected in a number of countries and is causing concern as it appears to be spreading rapidly. The new Omicron subvariant has been named Orthrus, after a two-headed dog from Greek mythology.
The last variant was codenamed Kraken, for a seabeast from northern European legends. Orthrus, designated CH 1.1, has been found to have a mutation that was found in the Delta strain of Covid - which could be helping it beat the vaccines.
The mutation - which increases the virus's ability to defeat vaccines - was not found in Omicron.
It has been detected in 66 countries including the USA, Thailand, India, China and Australia as well as the UK. Between them Kraken and Orthrus now make up 40% of all Covid cases in the UK, according to the UK Health Security Agency.
The latest figures show Covid cases continue to fall in the UK - but not among school-aged children.
But researchers at Ohio State University said Orthrus's ability to evade immunity is 'extraordinary'.