By Digital Producer Suzanne Elliott
The ever-changing coronavirus has spawned yet another Omicron sub-variant that is behind a surge in Covid cases in India.
Scientists say the variant, BA.2.75, may be able to spread rapidly and dodge immunity from vaccines and previous infection.
Since Omicron emerged at the end of 2021, it has developed several mutations. Currently, BA.5 is the dominant variant globally and is behind rising infections in the UK having started gaining ground in June.
We take a look at the latest Covid sub-variant that could take hold in the UK.
What is Omicron BA.2.75?
The Omicron variant of SARS-CoV-2, which was first detected in South Africa, carries over 30 mutations in its spike protein, according to a paper published in Nature.
Its parent lineage is BA.2, which swept across the country earlier this year.
The lead author of the paper, Prof. Ravindra Gupta, Professor of Clinical Microbiology, said that they discovered from the work they did that the virus likely evolves in different people or different groups of individuals.
"We were one of the first groups to show that the way you get multiple mutations is the virus evolving in a single person, often if they're immune-compromised.
"So, we believe BA.2.75 evolved in a person, just like BA.2 would have come from a single person. Each of these new lineages is probably evolving in individual people infected with different variants. It's not just the result of it (the virus) bouncing around between different people."
Is Omicron BA.2.75 more transmissible?
Virologists think that, yes, it could be more transmissible.
“It’s still really early on for us to draw too many conclusions,” said Matthew Binnicker, director of clinical virology at the Mayo Clinic in Rochester, Minnesota.
“But it does look like, especially in India, the rates of transmission are showing kind of that exponential increase." Whether it will outpace BA.5, he said, is yet to be determined.
Where has the variant been found?
According to the Pango website - used by researchers and public health agencies worldwide to track the transmission and spread of SARS-CoV-2 - the subvariant is mostly in India where 76% of infections are found.
It’s also been detected in about ten other countries, including the UK (home to 8% of the world's BA.2.75 infections), Australia, Germany and Canada. There has also been a handful of cases identified in the US.
How does it differ from other Omicron variants?
A large number of mutations of this variant are raising concerns among scientists. Some of those mutations are in areas that relate to the spike protein and could allow the virus to bind onto cells more efficiently.
These genetic tweaks may also make it easier for the virus to bypass antibodies - either from a Covid vaccine or an earlier infection.
Will the Covid vaccines work against BA.2.75?
Experts say vaccines and boosters are still the best defence against severe illness. Everyone over the age of 50 will be offered a fresh Covid-19 jab this autumn, to boost protection ahead of possible further waves of the virus, the UK Health Security Agency announced on Friday.
Could the sub-variant change the course of the pandemic - again?
Scientists say the emergence of BA.2.75 hot on the heels of BA.2 is another reminder that coronavirus is continually evolving in its bid to continue to infect. We may be trying to move on from the virus, but it is determined to follow.
The World Health Organisation warned Covid cases have tripled across Europe in the past six weeks, accounting for nearly half of all infections globally. It says hospitalisation rates have also doubled, although intensive care admissions remain low. This surge is driven by BA.5 but with another variant looming another peak could be around the corner.
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Is it more lethal than BA.2 or BA.5?
It is unclear whether BA.2.75 could cause more serious disease than other Omicron variants but Professor Paul Hunter, Norwich Medical School, University of East Anglia says it "doesn't as yet appear to be any more lethal than any of the previous waves.
"It seems, touch wood, to be following the pattern that we've seen this year, that each subsequent wave actually is less lethal and less harmful than the previous wave and I hope that continues, although there is no absolute guarantee that that would be the case," he said.
Prof Mark Woolhouse, Professor of Infectious Disease Epidemiology, University of Edinburgh said it was too soon to categorise BA.2.75 as a variant of concern but that it was being watched closely.
"We do need to continue to be very vigilant and to make rapid assessments of whether we pose a greatly increased threat from what we've seen before, but there's no indication so far that that's the case."
Prof. Gupta said because the mutations each have their own key features it is often difficult to predict their outcomes - including how contagious it will be, how pathogenic it could be, which cells and tissues it will infect - just by looking at the mutation. Modelling how a variant, or sub-variant, will impact each country is also more difficult as immune rates - through previous infection or vaccines, as well as age and other factors, are different.
Prof. Gupta also points out that Omicron, in all its mutations, remains milder than Delta which infected the lower lungs and was a driver of more serious illness.
"We're always worried as to whether we might see variants heading back towards the Delta properties. We don't think that's the case at the moment because all of the Omicrons appear to be not very good at infecting lower lung cells."
Why does Omicron have so many sub-variants?
While we are seeing an explosion of Omicron sub-variants that we didn't see with Delta, Omicron continues to be milder. That does not mean Covid will continue to evolve to become milder (something that will not happen in the early stages of the evolution of SARS-COV-2, but that these mutations are following that pattern - to the surprise of scientists.
"Many of us are quite surprised that we're getting all these Omicron sub-variants coming along because we didn't really get very successful sub-variants of Delta... we never had a huge wave associated with them," Prof Gupta told ITV News.
"So what's interesting is that these subvariants of Omicron seem to be generating a lot of distinctiveness, in other words, each one looks very different, quite different to the immune system, which is why it causes breakthrough infections in people who've been vaccinated many times.
"Omicron seems to be really good at generating all these different sub-variants very quickly, and each of them has distinct mutations and causes waves of disease. It might be because Omicron has kind of found a very good recipe, in other words, a good sort of combination of mutations that gives us key parts, really solid base qualities, and then all it has to do is vary some things on top.
"But you know, in saying that, I've been saying we'll see something different from Omicron for a while, but we haven't seen it yet. So that remains to be seen," he says.