A “close relative” of the coronavirus variant, Omicron, has mutations that can change its behavior and has begun to outperform the most common COVID strain in parts of Europe and Asia.
The highly contagious Omicron variant of the Sars-CoV-2 virus, the most common form of which is known as BA.1, is currently the cause of almost all coronavirus infections worldwide, according to The Guardian.
Although COVID has already peaked in some countries, scientists are now tracking an increase in cases caused by a close relative of Omicron known as BA.2, which is starting to supplant BA.1 in parts of Europe and Asia. Below is what scientists know about the new coronavirus subvariant.
Globally, BA.1 accounted for 98.8% of sequenced cases submitted to the public GISAID virus tracking database as of January 25. But, according to the World Health Organization (WHO), several countries are reporting a recent increase in cases associated with sub-option BA.2.
In addition to BA.1 and BA.2, the World Health Organization lists two other sub-options under the umbrella of Omicron: BA.1.1.529 and BA.3. They are all closely related genetically, but each has mutations that can change their behavior.
Trevor Bedford, a computer virologist at the Fred Hutchinson Cancer Center in the US, has been tracking the evolution of Sars-CoV-2. On Friday, he tweeted that BA.2 accounts for roughly 82% of cases in Denmark, 9% in the UK and 8% in the US. He based his analysis on sequencing data from the GISAID database and case counts from the Our World in Data project at the University of Oxford in the UK.
The BA.1 version of Omicron was somewhat easier to track than previous versions. This is because BA.1 is missing one of the three target genes used in a conventional PCR test. Cases showing this pattern were considered by default to be caused by BA.1.
BA.2, sometimes known as the “invisible” subvariant, does not have the same missing target gene. Instead, scientists track it in the same way as previous variants, including Delta, tracking the number of virus genomes submitted to public databases such as GISAID.
Experts say that, as with other variants, BA.2 infection can be detected using home coronavirus test kits, though they cannot specify which variant is responsible for the infection.
Some early reports indicate that BA.2 may even be more contagious than the already highly contagious BA.1, but so far there is no evidence that it is more likely to escape vaccine protection.
Danish health officials estimate that BA.2 may be transmitted one and a half times more often than BA.1, based on preliminary data, although it probably does not cause more severe disease.
In England, a preliminary analysis of contact tracing from 27 December to 11 January by the UK Health Agency shows that household transmission is higher among contacts of people infected with BA.2 (13.4%) compared to other cases of Omicron (10, 3%). The agency found no evidence of a difference in vaccine effectiveness.
The critical question was whether people infected with wave BA.1 would be protected from BA.2, says Dr. Egon Ozer, an infectious disease expert at Northwestern University’s Feinberg School of Medicine in Chicago. This has been of concern in Denmark, he said, where some places where there have been high numbers of BA.1 infections have reported an increase in BA.2 cases.
If a previous BA.1 infection didn’t protect against BA.2, then “it could be something like a bactrian camel wave,” says Dr. Ozer. “It’s too early to say if that will happen.” The good news, he says, is that vaccines and boosters still “keep people out of hospitals and keep people from dying.”
Prof Seshadri Wasan, Covid-19 vaccine researcher at the Australian Science Agency (CSIRO), says the GISAID analysis showed that as of January 27, 10,811 BA.2 sequences (22 sequences) have been registered from around the world, including Australia , but 90% of the sequences were from three countries: Denmark (8357), India (711) and the UK (607).
“For now, data from our Danish colleagues shows that while the virus may be spreading faster, there is no evidence of it getting stronger,” the scientist said. “It is therefore important to remain calm and continue existing measures such as vaccinations, including boosters, and adherence to social distancing, mask wearing and local regulations.”