A Covid-19 variant 'mutation' called Eris has led to certain scientists calling for the return of face masks.

Latest data shows the Omicron subvariant now accounts for 1 in 10 Covid cases - while the number of people recorded with the virus jumped from an estimated 3.3 per 100,000 to 7.2 in the space of less than a month.

But a brand new sub-strain, which has not yet been formally named but is referred to as 'BA.6', has fueled fears that echoes from 2020 may be around the corner.

While it has only been found in two countries so far, Denmark and Israel, one expert has claimed the new sub-strain is already showing an alarming tendency to mutate and alleges it has left a number of her peers concerned - prompting calls for masks.

Dr Trisha Greenhalgh, a primary healthcare expert at the University of Oxford, wrote on Twitter: "My various science WhatsApp groups are buzzing. Genetic lineage clips and diagrams flying back and forth. I understand little of the detail but it looks like it's once again time to MASK UP."

Professor Christina Pagel, a mathematician from University College London who is a sitting member on the Independent SAGE group, meanwhile said on the social media platform that it was "very very early days" but conceded that the variant has "LOT of new mutations that makes it v different to previous Omicron strains".

She added that this meant it was "potentially more able to cause a big wave", as per the Mirror.

In an opinion piece in the British Medical Journal on Tuesday, the professor stated that it was "reasonably certain that we have entered another Covid-19 wave" - though stressed it was "unlikely that this wave will cause a large surge in hospital admissions or deaths" because of the UK's high rate of vaccinations.

She added that one of her main fears was that Covid infections could create strain on the NHS by occurring at the same time as influenza infection and respiratory syncytial virus, as seen last winter.

Professor Pagel said there was also the "less likely" scenario of a new, undiscovered variant emerging, which could overwhelm people's existing resistance to the virus.

No official guidance for face masks has been issued by government or public health authorities in the UK, and the legal requirement to wear a face covering ended on January 27, 2022.