SINGAPORE - Singapore's first case of the AY.4.2 Delta subvariant has been confirmed in one imported Covid-19 case as at Tuesday (Oct 26), the Ministry of Health said on Thursday night.

The subvariant, also known as the Delta Plus variant, is a mutation of the Covid-19 Delta variant. It is a combination of the AY.4 Delta variant and the S:Y145H spike mutation.

The Health Ministry said there was no evidence of spread to the community from the case.

"While its effects are still being studied, AY.4.2 is currently expected to be similar to other Delta subvariants in terms of transmissibility and severity of illness," it added.

The subvariant is classified by the World Health Organisation as a variant of interest, but not a variant of concern.

The BBC reported that according to experts, there was no indication that the AY.4.2 subvariant is more infectious or more dangerous than the Delta, but tests are ongoing.

More than 6 per cent of all cases of the AY.4.2 subvariant so far have been reported in Britain.

Data from the GISAID virus reporting database also showed that cases of the subvariant have been reported in the United States, Canada, Australia and parts of Western Europe.

Newsweek reported that Australia and Japan had seen only one case each as at Oct 19.

University College London professor of computational systems biology Francois Balloux said the AY.4.2 subvariant has yet to be observed driving any recent increase in case numbers in Britain.

"As AY.4.2 is still at fairly low frequency, a 10 per cent increase in its transmissibility could have caused only a small number of additional cases," he said.

"This is not a situation comparable with the emergence of Alpha and Delta that were far more transmissible (50 per cent or more) than any strain in circulation at the time," he added.