LONDON - It has been nearly three years since Covid-19 was first detected, and changed the world.

The virus that shut down the world would go on to mutate into new variants after it emerged in Wuhan, China in December 2019.

Omicron was the last major variant, identified in November last year but scientists are already looking at what could replace it - Pi.

The Omicron variant initially caused huge concern around the world, not least because it was found to be highly transmissible and the 32 mutations to its spike protein suggested it might resist current vaccines.

But 12 months later, Covid cases are now beginning to fall after a mild autumn wave driven by a cluster of Omicron subvariants, which virologists described as “Omicron’s grandchildren.” These include the BQ.1 and BA.2.75.2 sub-variants, as well as XBB.