Face masks should be worn again on public transport to stop the spread of super-infectious Covid variant Arcturus, experts claimed.
The subvariant has been spreading across the globe, causing mask laws to be reintroduced in India, where five Brits have died with thr infection.
Arcturus, known as XBB.1.16, is on the rise in Australia now too, with UK health chiefs monitoring it closely.
In the past, new variants and subvariants led to increases in transmissibility or severity of the infection.
Now Professor Stephen Griffin, chair of Independent SAGE, said people should go back to regularly testing as well as wearing masks.
He told MailOnline: “This may seem like a throwback to last year, but the reality is the virus continues to do harm and those least able to cope continue to suffer.
“In the absence of population-scale mitigations... the focus remains upon individual risk which is, for many, now much lower.
"If [the] Government won’t act to enable everyone to 'live' with Covid, vulnerable people will continue to require precautions and, ideally, others will act with an appropriate level of altruism."
XBB.1.16 emerged from two previous potent strains of Omicron, BA.1 and BA.2, which posed serious issues for the UK.
Scientists flagged the new strain's "advantage" early on, with UKHSA first monitoring it on March 6.
It acquired three additional spike mutations which were suggested to have increased its transmissibility.
The identification of these spikes precluded a sharp increase in Arcturus cases globally, and particularly in India, which accounted for over half of the strain’s cases globally.
As things stand, there are 135 Arcturus sequences in the UK, believed to be around 104 cases as some people have been sequenced twice.
The median age for these cases was 74, continuing the trend of older Brits being more at risk, with 54 men and 50 women having caught it.
Across the UK, the strain is present in every country and region apart from the North East, being most prevalent in London, the North West and South East.
But the majority of the infections in the North West all came about in mid to late March, on the same day, suggesting it had spread at a large event.
The East of England recorded the country’s first Arcturus case and most recently it has been recorded in the North West once more, and London, according to the most recently available data.
