Stealth Omicron COVID Variant BA.2 That May Spread Faster Found in at Least 40 Countries

The Omicron BA.2 sub-variant, also dubbed "stealth Omicron," has been detected in at least 40 countries worldwide.

BA.2 has caught attention in recent days as it has been responsible for an increasing proportion of Omicron infections compared to the BA.1 lineage that has been the dominant Omicron type so far.

Labs in countries including Denmark and Norway have reported that the sub-variant has been gaining ground, accounting for nearly half of all COVID cases in the former as of January 20, marking a sharp increase in recent weeks.

Virologists say that there is much to learn about BA.2, but it appears the sub-variant may have a transmission advantage over BA.1.

In a press release issued last Friday, the U.K.'s Health Security Agency (HSA) said that BA.2 had been classified as a variant under investigation (VUI) due to international and domestic cases, adding that BA.2 appears to have an increased growth rate compared to BA.1, based on early analysis.

However, the HSA stated that the proportion of BA.2 cases in the country compared to BA.1 was "currently low" and that further analysis was needed to determine the significance of the sub-variant and its mutations.

"So far, there is insufficient evidence to determine whether BA.2 causes more severe illness than Omicron BA.1, but data is limited and UKHSA continues to investigate," said Dr Meera Chand, COVID-19 Incident Director at the HSA.

Effectiveness of Vaccines

A press release from Denmark's Statens Serum Institut (SSI) infectious disease research institution last week stated that it is expected that vaccines will continue to have an effect on severe illness caused by BA.2

A total of 40 countries had uploaded BA.2 sequences to the virus sequencing database GISAID since November 17, the HSA said last Friday. Outbreak.info, an online tool that presents COVID statistics using GISAID data, put that figure at 49 as of Monday.

One notable aspect of BA.2 is that it lacks a genetic characteristic that scientists had used to identify Omicron cases previously—giving credence to its "stealth Omicron" monicker.

However, Cornelius Roemer, a computational biologist at the University of Basel in Switzerland, tweeted last week that BA.2 is still detectable on PCR tests and branded news reports to the contrary as "totally wrong."

"Depending on the PCR test used it may not look like BA.1 (the other Omicron). But it will still give a positive result," he wrote.

According to GISAID on Monday morning, a total of 12,842 BA.2 sequences had been uploaded to its database from around the world. Some 67 of those were reported from the USA.