Omicron subvariant could be 1.5 times more infectious, but not more severe

There is no evidence that the BA.2 variant causes more disease, but it must be more contagious,

Danish Health Minister Magnus Heunicke said on Wednesday in a national address, Reuters reported.

The BA.2 sub-strain was first detected in China a couple of weeks ago and the general view is that it has originated in India.

The BA.1 lineage currently accounts for 98% of all cases globally but in Denmark has been pushed aside by BA.2, which became the dominant strain in the second week of January.

BA.2 cases have also been registered in Britain, Sweden and Norway, but to a much lesser extent than in Denmark. The UK Health Security Agency has designated BA.2 a variant under investigation, saying it could have a growth advantage. 

In mid-January, Israel detected some 20 cases of a new sub-variant, discovering that it contains more mutations than the original Omicron and may be more violent.

Preliminary calculations suggest BA.2 could be 1.5 times more infectious than BA.1,

Denmark's top infectious disease authority, Statens Serum Institut (SSI), said in a note on Wednesday.

However, an initial analysis by the institute showed no difference in the risk of hospitalisation for BA.2 compared to BA.1.

There is some indication that it is more contagious, especially for the unvaccinated, but that it can also infect people who have been vaccinated to a greater extent,

SSI's technical director Tyra Grove Krause said at the briefing.

What you need to know about BA.2

The UK Health Service Agency (UKHSA) has designated BA.2 as a “variant under investigation”, saying that it is a level below the status of Omicron, marked a “variant of concern” by the WHO.

“As per UKHSA, 40 countries had reported BA.2 sequences, with the most in Denmark, followed by India, Britain, Sweden and Singapore,” said Dr Mrinal Sircar, director oof Pulmonology and critical care at Fortis Hospital, Noida, India.

While the BA.2 strain is being attributed to faster infection, doctors dismiss the possibility of it being a more severe strain than the present Omicron variant. There is likely to be minimal differences in vaccine effectiveness against BA.1 and BA.2,” Dr Sircar told indianexpress.com.

While the sub variant does not escape an RT-PCR test, “the way the variant was confirmed was by seeing if there was a S gene drop out for BA.1. In BA.2, there is no S gene drop out, it would be difficult to confirm if it is BA.2 or some other variant without a full genome sequencing,” stated Dr Sircar.

The RT- PCR tests done in the labs detect the spike gene (a protein that showcases new variations than the old virus) through sequencing. Though various experts believe that the BA.1 sub-strain may sometimes escape the RT-PCR test, but as of now, that is the only gold standard tests available and do not pose any difference in any of the mutated variants. 

According to the reports by various experts and radiologists worldwide, the current testing kits are designed with high sensitivity and pick up rate to detect all the variants.

Cover photo: Getty Images.