SINGAPORE - Two local Covid-19 cases have been confirmed to be infected with a new Omicron sub-variant called BA.2.12.1 - a descendant of the BA.2 version of Omicron, which drove Singapore's Omicron wave.

The new version was detected through active monitoring of the Covid-19 situation and genetic sequencing, said the Ministry of Health (MOH) on its website on Thursday night (April 28), alongside its daily update on the local Covid-19 situation.

MOH added that the two individuals self-isolated after testing positive for Covid-19.

According to Gisaid, an online open-access repository for genomic data on viruses, three cases with the sub-variant have been detected here, with the first recorded in mid-April. 

The BA.2.12.1 is currently not on the World Health Organisation's list of variants of concern or interest, or variants under monitoring.

Since March 15, more than 98 per cent of local Covid-19 cases have been infected with the BA.2 sub-variant, MOH has said previously.

Preliminary studies show that BA.2 is more transmissible compared with the original Omicron sub-variant known as BA.1.

However, all the Omicron sub-variants are highly contagious, but less deadly compared with Delta or earlier variants.

The New York Times (NYT) reported two weeks ago that BA.2.12.1 and another sub-variant accounted for more than 70 per cent of new cases in central New York state last month.

But the new versions do not appear to cause more severe disease than previous Omicron variants, reported NYT.

Dr Sebastian Maurer-Stroh, executive director of the Agency for Science, Technology and Research’s Bioinformatics Institute, said: “The BA.2.12.1 sub-variant has been growing specifically in North America and could become dominant there in the near future.” 

Dr Maurer-Stroh is part of the global team that maintains Gisaid.

As at mid-April, the BA.2.12.1 has been detected in more than 40 countries.

Dr Maurer-Stroh said there is no experimental data on the new sub-variant’s transmissibility, or whether it is more contagious compared with BA.2.

He added that there should not be specific concern about any single Omicron variant or sub-variant here as vaccination levels are high in Singapore.

“There are many similar variants circulating concurrently as part of the natural evolution of this virus and all of them are monitored closely.”