Covid Scotland: Cases of BA.2.75 'Centaurus' variant found

The true figure is likely to be substantially higher as only a fraction of positive PCR results go forward for sequencing, and Covid testing is no longer routinely available in the community.

Virologists have described BA.2.75 as a "wildcard", and suggested that it could displace the UK's currently dominant BA.5 Omicron variant.

ANALYSIS: Omicron, 'Centaurus', and what's next for Covid? 

It was first identified in India in early May, where it appeared to be outcompeting other Omicron sublineages, and has been classified as a variant of interest by the World Health Organisation while monitoring continues.

The European Centre for Disease Prevention and Control (ECDC) designated BA.2.75 as a “variant of interest” on July 7, with the UKHSA following suit and officially describing it as a "variant under investigation" on July 18.

This means there is not yet enough evidence to upgrade it to a variant of concern - for example if it was shown to have substantially increased transmissibility, virulence, or immune evasion.

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BA.2.75 was dubbed Centaurus on Twitter, but remains part of the Omicron family.

An offshoot from BA.2, it has nine new mutations - including eight relating to the spike protein which could make it even harder for Covid antibodies to latch on and prevent infection.

This would not affect cellular immunity from T cells, which protects against more severe disease, and there is currently no evidence that BA.2.75 is any more harmful than existing strains.

Dr Tom Peacock, a virologist at Imperial College London, who was the first to identify Omicron as a potential concern back in November 2021, said: “It’s hard to predict the effect of that many mutations appearing together – it gives the virus a bit of a ‘wildcard’ property where the sum of the parts could be worse than the parts individually.

“It is definitely a potential candidate for what comes after BA.5."

However, writing in the Conversation, Ben Krishna, a researcher in immunology and virology at Cambridge University, said there was not yet "clear evidence" proving that BA.2.75 is spreading faster than other strains.

He stressed that there had been no big increase in deaths or hospitalisations linked to 'Centaurus' in India, and that its growth advantage may only have applied in regions where it wasn't competing against BA.5.

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He added: "It seems to have shown an increase which has levelled off or even dropped relative to a few weeks ago. If this is the case there’s a chance it might even fizzle out in another few weeks.

"But, if BA.2.75 does have some immune evasion properties, it could cause another wave through the UK and elsewhere. Still, this would likely spike and then fizzle out like alpha, delta and omicron BA.1."

Meaghan Kall, an epidemiologist at the UKHSA, cautioned that the virus could be running out of new potential new hosts to have much impact given the Omicron BA.1, BA.2 and BA.5 waves of the past six months.

Writing on Twitter, she said: "By the time BA.5 wave is done approx 75% of English [population] will have been infected with Omicron.

"Leaves very little niche for BA.2.75 to make a ripple let alone a wave.

"That said BA.2.75 may well cause new waves in countries where BA.4/5 haven’t yet dominated, such as India, and severity is as yet unknown, so still worth watching."

It comes as the latest update from Public Health Scotland reports that the Omicron BA.5 variant is now responsible for around 70% of Covid infections in Scotland, based on data up to July 17.  

However, there are also signs that the BA.5 wave has now peaked in Scotland.

BA.5 (light blue) is the dominant variant in Scotland, while BA.4 is levelling off. There are also signs of a possible decline in cases (Source: Public Health Scotland)

In the week ending July 24, a total of 8,911 positive Covid cases were reported in Scotland, of which 2,053 (23 per cent) were reinfections. 

This is down slightly on the previous week and, while based on very limited availability of testing, correlates with a decline of Covid patients in hospital.  

Number of new Covid cases reported in Scotland Source: Public Health Scotland

The PHS report states: "There has been a recent decrease in cases reported to PHS, including the number of Omicron BA.5 in Scotland.

"This follows a sustained increase in cases, primarily of the sub-lineage Omicron BA.5 in Scotland.

"Omicron BA.4 has remained stable over the last few weeks after an initial increase.

"Figure 2 shows the rapid increase in the proportion of sequences of BA.5, and the recent stability of proportion of sequences of BA.4 relative to other variants.

"Omicron BA.5 is now the predominant variant in Scotland, surpassing Omicron BA.2 and accounting for 70% of newly reported sequenced cases."

The most recent surveillance by the Office for National Statistics estimated that one in 15 people in Scotland had Covid in the week ending July 14. 

This was up from one in 16 the week before, but continues to show a slowdown in the spread of the virus which had previously increased rapidly from a rate of one in 50 at the end of May to one in 18 by the week ending June 24.  

The number of Covid positive patients in hospital has begun to decline (Source: PHS)

Figures updated today also show that the number of Covid positive patients in hospital has declined by 8.6% from 1,733 on July 17 to 1,584 by July 24. 

The hospital data - which acts as a gauge for community prevalence of the virus - indicates that the BA.5 wave may have peaked around July 13, when there were 1,804 Covid patients in hospital. 

This compares to a peak of 2,406 on April 2, at the height of the BA.2 wave. 

Current analysis suggests that only around a third of the Covid patients in hospital have been admitted with the infection as their primary diagnosis.