A new Covid variant that is causing concern among scientists due to its large number of mutations has been detected in London. The variant, named BA.2.86, has been detected through genetic sequencing, although only a handful of such sequences have so far been reported. The first was reported in Israel, with the variant since being detected in Denmark and the US. The UK Health Security Agency (UKHSA) confirmed on Friday that the variant had been detected in the UK. Dr Meera Chand, the deputy director of UKHSA, said: “We are aware of one confirmed case in the UK. UKHSA is currently undertaking detailed assessment and will provide further information in due course.” According to a risk assessment published on Friday by UKHSA, the UK case had no recent travel history, suggesting established international transmission and a degree of community transmission within the country – with more information on UK transmission expected in the next week or two. It said the similarity of the genetic sequences in different countries implied a relatively recent emergence and rapid growth, although this remained a tentative analysis given the small number of sequences. At present, the agency said, there was not enough data to assess the relative severity or degree of immune escape of BA.2.86 compared with other variants in circulation. The World Health Organization announced on Thursday it was designating BA.2.86 a “variant under monitoring” – while the US Centers for Disease Control and Prevention (CDC) has similarly reported it is keeping a close eye on the variant after it was discovered in Michigan. As well as outstanding questions over the severity of the variant, it is unclear whether it will become the dominant form of the virus. Its many genetic changes – it has more than 30 mutations in the spike protein relative to the current predominant variant – and its detection in several countries have put scientists on alert. Prof Francois Balloux, director of the UCL Genetics Institute, said BA.2.86 was the most striking Covid strain the world has witnessed since the emergence of Omicron. “The most plausible scenario is that the lineage acquired its mutations during a long-term infection in an immunocompromised person over a year ago and then spread back into the community,” he said. “BA.2.86 has since then probably been circulating in a region of the world with poor viral surveillance, and has now been repeatedly exported to other places in the world.” Balloux added that how well the new variant fared relative to other Omicron subvariants would become clearer in the coming weeks. “Nothing is known at this stage about its intrinsic transmissibility and virulence,” he said. “A priori, it is not expected to behave differently from current Omicron strains in circulation. “Even in the worst-case scenario, where BA.2.86 caused a major new wave of cases, we are not expecting to witness comparable levels of severe disease and death as we did earlier in the pandemic when the Alpha, Delta or Omicron variants spread,” he added, noting that most people have now been vaccinated, infected with Covid, or both. But, he said: “It remains that a large wave of infection by BA.2.86, or any future comparable variant, would be an unwelcome event.” Prof Tom Wenseleers, an evolutionary biologist at the Catholic University of Leuven in Belgium, agreed. “I would be very surprised if the high levels of population immunity would not keep on protecting us well against severe disease,” he said. “But all in all I would say it is relatively likely that this variant may cause an infection wave, even though right now it is impossible to say exactly how large, and also what the impact on hospitalisations will be.” Prof Rowland Kao, an epidemiologist at the University of Edinburgh, said the appearance of a potential new variant of concern was not a surprise. “But,” he added, “it doesn’t mean we are well-prepared for it now.” Among other issues, Kao said Covid appears to be on the rise once more, with hospitalisations also increasing. That, he added, was without evidence the new variant was a factor. “We should expect that the usual combination of autumn return to school and university and work play a part, as well as possibly the seasonal factors,” said Kao. “Plus the bulk of vaccinations have now been some time ago, and even the most vulnerable are likely approaching the point where immune protection is fading.” BA.2.86, Kao said, could add to the pressures, noting that one worry was whether the variant would evade past immune protection and was sufficiently different as to make vaccines less effective. “There is a good chance we are in for a bumpy ride, which will only be bumpier if this variant presents any added twists,” he said.