As the Omicron variant of Covid-19 eases its grip on countries around the world, a sub-variant of the same is causing concern among health experts, especially in South-East Asia.

The BA.2 lineage of the Omicron variant has been steadily increasing in many countries, including India, China and Pakistan, according to the latest World Health Organisation report.

As new lab studies have revealed that Omicron subvariant BA.2 could cause severe illness like Delta and previously identified COVID variants, epidemiologist Eric Fang voiced that it needs to be upgraded to Variant of Concern.

The three crucial things about the subvariant BA,2, also known as stealth Omicron, that the Japanese team has identified are - BA.2 may have features that make it capable of causing serious illness, it shows immune escape properties just like sub-variant BA.1. Further stealth Omicron is resistant to treatments like sotrovimab, the monoclonal antibody.

US top epidemiologist Dr Eric Feigl-Ding on Sunday stressed that new lab experiments from Japan show that BA.2 may have features that make it as capable of causing serious illness as older variants – including Delta.

He further suggested that the WHO needs to upgrade the BA.2 sub-strain as a variant of concern.

"BA.2 is seriously bad news. It’s both faster transmission than BA2 and if it’s truly more severe and as evasive against prior immunity including BA.1 old #Omicron immunity— then it’d be the worse of 4 worlds (sic)," he tweeted.

According to a lab study in Japan, BA.2 sub-strain is ‘not only faster at spreading, but also likely to cause more severe disease.’

While the first sequences of BA.2 were submitted from the Philippines – and we have now seen thousands of cases, including in the United States, the UK, and some in Australia – its origin is still unknown.

The exact properties of BA.2 are also still being investigated.