The BA.2.75 variant – nicknamed “Centaurus” – was first spotted in India in early May. Here, cases have since skyrocketed – and apparently faster than those of the highly contagious BA.5 variant, which is also present in India, and is rapidly replacing the previously dominant BA.2 variant in many countries. BA.2.75 has also since been detected in about 10 other countries, including the UK, US, Australia, Germany and Canada. The European Center for Disease Prevention and Control (ECDC) labeled it a “variant under surveillance” on July 7, meaning there is some evidence it could be more contagious or associated with more severe disease, but the evidence is weak or have not yet been evaluated. The World Health Organization (WHO) is also closely monitoring the new variant, although its chief scientist Dr Soumya Swaminathan said there were not yet enough samples to assess its severity. In addition to its apparent rapid growth and wide geographic spread, virologists have been taken aback by the sheer number of additional mutations BA.2.75 contains, relative to BA.2, from which it is likely to have evolved. “This could mean that it had the opportunity to evolve an advantage over an already successful lineage of viruses,” said Dr Stephen Griffin, a virologist at the University of Leeds. “It’s not so much the exact mutations as the number/combination,” said Dr. Tom Peacock, a virologist at Imperial College London, who first identified Omicron as a potential concern in November 2021. “It’s hard to predict the effect of so many mutations appearing together – it gives the virus a ‘wild card’ quality where the sum of the parts could be worse than the parts individually. “It’s definitely a potential candidate for what comes after BA.5. Otherwise, it’s probably something we’ll have next, i.e. a “variant of a variant”. Even if it doesn’t take off in other countries, its growth in India suggests it’s likely to be a problem there, at least, Peacock added. “It’s clearly growing quite well in India, but India doesn’t have a lot of BA.5 and it’s still very unclear how well it does against [that].” Griffin cited this as yet another example of the virus’s impressive ability to tolerate changes in its spike protein – the part it uses to infect cells and on which most Covid vaccines are based. “This time last year, many were convinced that Delta represented an evolutionary peak for the virus, but the emergence of Omicron and the massive increase in antibody variability and evasion is a sign that we cannot as a population follow a plan that looks like influenza to keep pace with the evolution of the virus,” Griffin said. In addition to vaccines, longer-term plans should include variant-agnostic measures to prevent infections and reinfections. “This includes creating infection-resistant environments through improved ventilation, filtration or sterilization of indoor air, reasonable re-provision of lateral flow testing, and appropriate and supported periods of isolation that will truly reduce ongoing transmission,” he said.
