Stealth version of Omicron spreads to 40 countries

UK health authorities declare a sub-line ofOmicronis a "variant under investigation" after the number of positive cases increased.

Cases of the variant, known as BA.2, have been reported in 40 countries. Denmark has seen the largest increase in BA.2, accounting for nearly 50% of all new Covid-19 cases. In the UK, more than 400 cases of BA.2 have been identified since January 21.

There are concerns among scientists that BA.2 may be more contagious. But so far, there is too little information to draw any firm conclusions.

How is BA.2 related to Omicron?

Most Omicron infections are of the BA.1 variant, but the BA.2 subtype is also being detected around the world. BA.2 was first reported on December 6.

Illustration: Sciencefocus

BA.2 is very similar to BA.1 and both are considered Omicron. However, BA.1 can be detected by PCR testing when it lacks the S gene. Meanwhile, BA.2 has the S gene and requires gene sequencing, making it more difficult to detect.

"The significance of the changes in the virus genome remains uncertain. We need to carry out further analysis," the UK health agency said.

Impact of BA.2

The emergence of BA.2 in areas where BA.1 is dominant has led to concerns that the strain is more transmissible. However, scientists have stressed that there is not enough evidence to draw any conclusions.

In Denmark, BA.2 accounts for about 50% of cases. Hospitalizations do not appear to differ between the two Omicron strains, the State Serum Institute said.

Tom Peacock, a virologist at Imperial College London, said early data from Denmark and India showed BA.2 was not significantly different in severity from BA.1.

“There may be small differences in vaccine efficacy against BA.1 and BA.2,” Mr Peacock assessed.

“The nature of viruses is to evolve and mutate. So we will continue to see new variants emerge as the pandemic continues. Genomic surveillance allows us to detect and assess them,” said Dr. Meera Chand.