Omicron BA.2.7, the ‘Centaurus’ variant: How is it different?

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An emerging sub-variant of Omicron, BA.2.7, dubbed “Centaurus” on social media, is causing both concern and confusion among people around the world. Why the astronomical nickname, what do we know about it, and is there really cause for concern? Here’s what the data and the experts have to say.

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A new sub-variant, dubbed “Centaurus”, is spreading rapidly. What do we know about this? Image credit: picture alliance/Getty Images.

Our lives were much simpler in many ways at the start of 2020. We only had one variant of SARS-CoV-2, the wild type, and we had no idea what the COVID pandemic- 19 was in store for us.

When scientists began to detect new variants of interest or concern, they first dubbed them after the places where they had emerged.

The World Health Organization (WHO) has tried to officially designate variants with names from the Greek alphabet in an effort to curb racist and xenophobic associations, such as those seen when SARS-CoV-2, the virus that causes COVID-19, was first detected in China.

The ‘Kent variant’, first identified in the UK, thus became the Alpha variant, and this pattern continued with the Beta variant, first identified in South Africa, and so on.

The current dominant variant in countries around the world is the Omicron variant. However, a number of subvariants have been detected within the Omicron lineage in recent months.

One of them, named BA.2.75 in the Pangeo lineage system used by virologists and the WHO, was nicknamed Centaurus on the back of a single Tweeterwhich has spread surprisingly well.

Many people and headlines now refer to the Centaurus variant the same way they referred to the Delta and Beta variants, as if that were its official name.

The WHO has not yet designated BA.2.75 as a variant of concern in its own right, although it is currently monitoring it. The European Center for Disease Prevention and Control (ECDC) designated it as a “variant under surveillance” on July 7, 2022 because it was detected in European countries, including the United Kingdom and Germany.

Experts first detected this variant in India in May, where it is believed to be spreading faster than other Omicron sub-variants.

Spyros Lytras, PhD researcher in virology at the University of Glasgow’s Center for Virus Research, said Medical News Today:

“I agree with the current WHO approach of not awarding new [variants of concern] to Omicron sub-variants so far. The appearance of Omicron was a very important event in the evolution of the virus and the progress of the pandemic and other such major “leaps” are expected in the future. As such, if we were to name each sub-variant of Omicron with a new Greek letter, we would undermine the importance of Omicron as a group of sub-variants.

The so-called Centaurus variant is not the first Omicron sub-variant to be detected, nor the only sub-variant monitored at the moment.

BA.4 and BA.5 and others are also subvariants of Omicron that are closely watched by public health organizations, and a study in Naturepublished as an unedited manuscript, showed that they could both escape immunity conferred by infection with the original Omicron variant, or any vaccine that might be based on it.

This emerging subvariant is so new that only 400 genomic sequences of it have been made available to date, explained Dr. Ulrich Elling, research group leader at the Institute of Molecular Biotechnology in Vienna, Austria, where he supports genomic surveillance of COVID-19.

Already, experts have determined that BA.2.75 has nine mutations, including eight new ones in the domain of the spike protein-coding genome, in addition to the 29 BA.2 mutations already present in the variant from which it evolved. As “immune evasion is the primary selective force, we should now expect BA.2.75 to primarily affect immune evasion,” Dr. Elling said.

Very little has been published about the variant yet, although a team in Beijing has investigated what the individual effects of each of the mutations might be and shared a preview of some of their findings.

Dr Elling said: “What the data indicates is that BA.2.75 is particularly suited to overcoming the immune protection generated by Delta whereas it is similar to other Omicron lines after vaccination. However, it must be said that the data is very preliminary and based on few patients, as well as generated with a pseudovirus as opposed to the true BA.2.75 isolates, so we really have to wait for further results.

These data suggest that BA.2.75 has a higher affinity for ACE2 receptors, the receptor found in many human tissues to which the SARS-CoV-2 virus binds to enter human cells and replicate.

Another study, the results of which were shared as a preprint by a team in Japan, generated pseudoviruses harboring the spike proteins of BA.2.75, BA.4, BA.5, and BA.2, and exposed them to monoclonal antibodies that are used as a treatment for people with COVID-19, but would be less effective if the variant were able to evade the antibodies it contains.

Lytras noted in this regard that “[s]Some preliminary lab results suggest that BA.2.75 has a slightly different immune evasion phenotype than BA.4 and BA.5, but I don’t think there is enough experimental or epidemiological evidence yet to support BA. 2.75 is – or will be – cause for concern.

The current level of testing is also too low to say whether the BA.2.75 variant would become the dominant variant in the next wave, Dr Elling said.

“Anyway, the big open question is whether we will stay in the Omicron clade this winter or whether an old variant makes a revival. Delta is still detected for example and, as we know, the virus remains hidden in immunocompromised patients for more than a year before resurfacing as a new variant. A year ago there was Delta everywhere, no Omicron,” he pointed out.

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