COVID-19: 'Centaurus’ Omicron variant? What we know so far

A new, highly-mutated coronavirus sub-variant has been nicknamed “Centaurus”. It’s a catchy name for the BA.2.75 sub-variant of the Omicron strain of COVID-19 that appears highly transmissible, and expected to dominate other variants.

The nickname is a throwback to a celestial body named after the father of the centaurs from Greek mythology.

Here’s what we know so far:

What is Centaurus? Is it an official name?

Centaurus is the unofficial name of the Omicron B.2.75 sub-variant of SARS-CoV-2, the virus that causes COVID-19.

All Omicron subvariants are considered "of concern”, according to the World Health Organisation (WHO).

How did “Centaurus” get its name?

In Greek mythology, Centaurus represents a centaur — a half-human-half-horse creature. Proxima Centauri (part of the triple-star Centauri constellation) is the closest star to earth than the next nearest Sun-like star.

The name was coined by an amateur Covid commentator called Xabier Ostale on Twitter to refer BA.2.75, and is now used by a number of media outlets.

His nickname has since taken off.

The emergence of Omicron BA.4 and BA.4 strains as well as Centaurus has triggered renewed calls to bring back masks and other protective measures.

Which countries have reported cases of the BA.2.75 variant?

BA.2.75 is new, only recently discovered in India, followed by 10 countries soon after. So far, the following countries have reported BA.2.75 (Centaurus) cases:

What sets BA.2.75 apart from other sub-variants?

BA.2.75 is a derivative of BA.2, but is quite apart from BA.4 and BA.5. The Spike is the most heavily-mutated protein in the Omicron family of variants.

Scientists have cited that Centaurus (BA.2.75) has at least 11 unique mutations from BA.5, thus making it “super contagious”?

This pattern is seen with BA.2.75, too. There are 36 mutated amino acids in the BA.2.75 Spike protein. With these mutations, it accounts for roughly 10% of the SARS-CoV-2 genome.

Why do new COVID variants or sub-variants keep emerging?

Nature published in April 2022 showing the the number of unique SARS-CoV-2 Receptor Binding Domain (RBD) variants “doubles” every 89 days. It’s the spike protein’s RBD that determines the success of infection.

While the understanding about the rapid pace of SARS-CoV-2 evolution is well established, but the long-term implications of this phenomenon is not fully yet understood.

One thing is clear: the rapid evolution of SARS-CoV-2 continues to challenge human defences.

Computational biologists like Carlos Duarte, who works for the Red Sea Research Centre (RSRC), King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, explained in their study that his doubling is followed by a process of "natural selection” — which then leads to the most infective variants challenging existing human defences (including previous vaccination or, prior infection).

How is the evolution of SARS-CoV-2 being tracked?

The WHO has stated it continues to monitor the sub-variant as it spreads. Confirmed cases due to BA.2.75 are relatively low, numbers are expected to increase in the coming weeks.

At the global level, the evolution of SARS-CoV-2 and its dynamics are monitored through real-time tracking of SARS-CoV-2 population genomics.

This is done through collaboration among scientists, including the so-called “mutation detectives” (phylogeneticists). Using open-source databases, this network of academics conduct a global genetic surveillance of SARS-CoV-2, and other pathogens of interest, or concern, and assigns them standard names based to the Greek letters.

Given the KAUST study, it’s now well understood that the faster mutation rate in the Spike protein of SARS-COV-2 — and of the Omicron strain in particular — increases its variability and antibody evasiveness.

This, experts say, suggests that health policy makers should reconsider following an influenza-like plan to keep pace with viral evolution within the population.

To prevent infections and reinfections over the long-term, they suggest the inclusion of “variant-agnostic” measures — including creating infection-resilient environments through improved ventilation, filtration, or sterilisation of indoor air, reprovision of lateral flow tests, and appropriate and supported isolation periods that will actually reduce ongoing viral transmission.