Scientists are now tracking a rise in cases caused by a close cousin known as BA.2, which is starting to outpace BA.1 in Europe and parts of Asia. What we know so far about the new subvariant is the following:
“Stealth” Subvariants
Globally, BA.1 has accounted for 98.8% of the indexed cases submitted to the public virus tracking database GISAID as of January 25. But several countries have recently been reporting an increase in the subvariant known as BA.2. World Health Organization,
In addition to BA.1 and BA.2, WHO lists two other subvariants under the Omicron umbrella: BA.1.1.1.529 and BA.3. All are closely related genetically, but each has mutations that can change their behavior.
Trevor Bedford, a computational virologist at the Fred Hutchinson Cancer Center who is tracking the evolution of SARS-CoV-2, wrote on Twitter on Friday that BA.2 accounts for about 82% of cases in Denmark, 9% in the UK and 8% of cases. represents. Case counts in the United States, based on their analysis of sequencing data from the GISAID database and from Our World in Data Project at the University of Oxford.
The BA.1 variant of the Omicron has been somewhat easier to track than the earlier variants. This is because BA.1 is missing one of the three target genes used in a typical PCR test. Cases showing this pattern were assumed by default to be due to BA.1.
BA.2, sometimes referred to as the “stealth” subvariant, does not contain 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.
Experts said that like other variants, an infection with BA.2 can be detected with coronavirus home test kits, although they cannot say which variant is responsible.
more permeable?
Some preliminary reports indicate that BA.2 may be more contagious than the already highly infectious BA.1, but there is no evidence yet that it is more likely to evade protection from the vaccine.
Danish health officials estimate that BA.2 may be 1.5 times more transmissible than BA.1, based on preliminary data, although it is unlikely to cause more serious disease.
In England, a preliminary analysis of contact tracing by the UK Health Protection Agency (HSA) from 27 December 2021 to 11 January 2022 suggests that household transmission is high among contacts of people infected with BA.2 (13.4%). ) compared to other Omicron cases (10.3%).
As of January 28, the HSA found no evidence of a difference in vaccine effectiveness.
An infectious disease specialist at Northwestern University Feinberg School of Medicine in Chicago, Dr. Egon Ozar said that an important question is whether people infected in the BA.1 wave will be protected from BA.2.
This has been a concern in Denmark, where high cases of BA.1 infection were seen in some places, which were reporting increasing cases of BA.2, Ozer said.
If prior BA.1 infection doesn’t protect against BA.2, “it could be a wave like a two-humped camel,” Ozer said. “It is too early to know whether 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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