What We Know About the Omicron BA.2 Subtype As U.K. Labels It Under Investigation

An Omicron sub-variant known as BA.2 is circulating in a number of countries, and virologists are still working to find out more about it.

The United Kingdom Health Security Agency (UKHSA) on Friday announced that the sub-lineage had been designated as a variant under investigation, though the country has so far seen a relatively low number of cases—426 as of Friday, Reuters reported.

On Thursday, Denmark's Statens Serum Institut (SSI), an infectious disease research institution, reported that the BA.2 sub-variant was "gaining ground" and was accounting for nearly half of all COVID cases in the country—a large increase from late 2021.

Norway, too, has reported that the BA.2 sub-variant is "increasing rapidly" in the country. It was detected in just seven cases on January 4 but had risen to a total of 611 by January 19, mainly in Oslo.

The Norwegian Institute of Public Health said in a report that "this edition of Omicron is growing strongly compared to the original Omicron, BA.1."

"The properties of the virus are not known other than that it is more contagious than BA.1 and increases correspondingly in Denmark and Sweden and may appear to take over BA.1 already," it added, translated from Norwegian.

It is still unclear exactly what difference, if any, BA.2 might make to the current situation in many countries. The Bloom Lab, which studies the evolution of viruses at the Fred Hutchinson Cancer Research Center, tweeted that the subvariant "shares many but not all mutations with Omicron."

Tom Peacock, a virologist at Imperial College, London, wrote in a tweet on Wednesday that BA.2 "may be some degree more transmissible" than the original Omicron variant but other information, such as disease severity, is still unclear.

He added he was "not sure" that the sub-variant would have a substantial impact on the current Omicron wave.

Data from Denmark so far has shown no differences in hospitalizations for BA.2 compared with BA.1, and while studies are ongoing to determine how well vaccines might work against the sub-variant it is expected that they will continue to have an effect on severe illness caused by BA.2, the SSI reported.

According to the virus genetic sequencing database GISAID, BA.2 has been detected in a number of other countries including the U.S., India, Vietnam, Sweden, South Africa and more, with a total of around 10,144 cases logged.

It is not unusual for viruses to mutate, and it is expected that new variants of SARS-CoV-2 will continue to emerge, Dr. Meera Chand, incident director at the UKHSA, said on Friday, according to Reuters.

COVID test
A health worker holds a COVID test swab in London in November, 2020. An Omicron sub-type called BA.2 is under investigation in the U.K. Leon Neal/Getty