The highly transmissible Omicron variant of the SARS-CoV-2 virus accounts for nearly all of the coronavirus infections globally. Scientists are now tracking a rise in cases caused by a close cousin known as BA.2, which is starting to outcompete BA.1, reports Reuters.
Globally, BA.1 accounted for 98.8% of sequenced cases submitted to the public virus tracking database GISAID as of Jan. 25. But several countries are reporting recent increases in the subvariant known as BA.2, according to the World Health Organization.
In addition to BA.1 and BA.2, the WHO lists two other subvariants under the Omicron umbrella: BA.1.1.529 and BA.3. All are closely related genetically, but each features mutations that could alter how they behave.
The BA.1 version of Omicron has been somewhat easier to track than prior variants. That is because BA.1 is missing one of three target genes used in a common PCR test. Cases showing this pattern were assumed by default to be caused by BA.1.
BA.2, sometimes known as a “stealth” subvariant, does not have the same missing target gene. Instead, scientists are monitoring it the same way they have prior variants, including Delta, by tracking the number of virus genomes submitted to public databases such as GISAID.
As with other variants, an infection with BA.2 can be detected by coronavirus home tests kits, though they cannot indicate which variant is responsible, experts said.
Is it more transmissionable?
Some early reports indicate that BA.2 may be even more infectious than the already extremely contagious BA.1, but there is no evidence so far that it is more likely to evade vaccine protection.
Danish health officials estimate that BA.2 may be 1.5 times more transmissible than BA.1, based on preliminary data, though it likely does not cause more severe disease. read more
The HSA found no evidence of a difference in vaccine effectiveness, according to the Jan. 28 report.
A critical question is whether people who were infected in the BA.1 wave will be protected from BA.2, said Dr. Egon Ozer, an infectious disease expert at Northwestern University Feinberg School of Medicine in Chicago.
If prior BA.1 infection does not protect against BA.2, “this could be sort of a two-humped camel kind of wave,” Ozer said. “It’s too early to know if that will happen.”
The good news, he said, is that vaccines and boosters still “keep people out of the hospital and keep people from dying.”
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