Scientists are monitoring an unusual increase in cases of BA.2, a new subvariant believed to be more transmissible than the Omicron variant.
The BA.2 subvariant is reportedly beginning to “compete” with BA.1, the more common form of the Omicron variant, in various regions of Europe and Asia after a spike in reported cases associated with this strain, Reuters reported on January 30.
According to the GISAID database, as of January 25, the BA.1 variant accounted for 98.8% of global Omicron cases. However, several countries are reporting a recent increase in the BA.2 subvariant, according to the World Health Organization.
Based on data analysis from GISAID and Our World in Data, Trevor Bedford, a virologist at the Fred Hutchinson Cancer Center, stated on January 29 that BA.2 currently accounts for about 82% of COVID-19 cases in Denmark, 9% in the UK, and 8% in the US.
Some early reports also indicate that BA.2 may be even more transmissible than BA.1, which is already known for its rapid spread. Danish health officials estimate that BA.2 could be 1.5 times more transmissible than BA.1, although it may not cause more severe illness.
The BA.2 subvariant appears in Denmark and several other countries. (Photo: DW).
In addition to BA.1 and BA.2, the WHO lists two other Omicron subvariants: BA.1.1.529 and BA.3. All are genetically closely related, but each variant has different mutations that may alter how they behave.
The BA.1 version of Omicron is somewhat easier to track than earlier variants because it lacks one of the three target genes used in standard PCR tests. By default, cases showing this pattern are assumed to be caused by BA.1.
BA.2, sometimes referred to as the “stealth” subvariant, does not share the same missing target gene. Instead, scientists are monitoring it in the same way they detected earlier variants, including Delta, by tracking the number of viral gene sequences submitted to public databases like GISAID.
Like other variants, infections caused by BA.2 can be detected using at-home COVID-19 tests, although they cannot specify which variant is responsible for the infection, experts say.
In the UK, preliminary analysis from December 27, 2021, to January 11 by the UK Health Security Agency (HSA) showed a higher household transmission rate for individuals exposed to BA.2 (13.4%). This rate for other Omicron variants was only 10.3%.
However, there is currently no evidence that the new variant is more likely to evade the “protective layer” of vaccines.
Another important question now is whether individuals previously infected with BA.1 are protected against BA.2, according to Dr. Egon Ozer, an infectious disease expert at the Feinberg School of Medicine at Northwestern University in Chicago.
If immunity following BA.1 infection does not protect individuals against BA.2, “this could be two burdens at once during this outbreak”, Ozer said. “However, it is still too early to know if that will happen.”
