Covid: what is the new BA.2 omicron sub-variant like and why do they call it “silent”?

The extremely transmissible omicron variant currently accounts for half of the world’s covid-19 infections.

But omicron is a general term to designate several closely related lineages of the SARS-Cov-2 coronavirus, the most common of which is BA.1

Now, more and more countries -especially in Asia and Europe- are reporting an increase in cases caused by the BA.2 lineage.

“Silent” subvariant

BA.2 is often referred to as a “silent” subvariant, because it lacks the genetic marker that researchers had been using to quickly determine whether an infection was most likely to be with the “regular” omicron (BA.1). , instead of the delta variant.

As with other variants, a BA.2 infection can be detected by a lateral flow test or PCR, but these tests cannot distinguish BA.2 from delta. Other tests are needed to be sure.

BA.2 appears to be more transmissible than previous variants, but fortunately, no data suggests it is more serious.

So how worried should we be about this variant?

Next, we tell you what is known about it.

What is the BA.2?

As viruses mutate into new variants, they sometimes divide or branch into sublineages. the variant delta, for example, consists of 200 subvariants different.

The same thing happened with omicron, which includes the lineages BA.1, BA.2, BA.3 and B.1.1.529.

BA.1 represents the majority of cases. According to the World Health Organization, nearly 99% of viral DNA submitted to the global GISAID database (as of January 25, 2022) was sequenced as this subvariant.

It is not clear where it originated, but first detected in November among sequences uploaded to the database from the Philippines.

Where is the BA.2 sublineage spreading?

Since November, 40 countries have added thousands of BA.2 sequences to the database.

According to the WHO, the subvariant is already becoming dominant in the Philippines, Nepal, Qatar, India, and Denmark. In some places, your growth has been abrupt.

India is another country where BA.2 is rapidly replacing the delta and omicron variant BA.1, according to molecular biologist Bijaya Dhak.

• Ómicron: 5 good news to end the year

The Philippines Department of Health (DOH) said the BA.2 sublineage was now prevalent in samples it received in late January.

And in England, more than 1,000 confirmed cases of BA.2 have been identified, according to the UK Health Security Agency (UKHSA).

It has been designated as a “variant under investigation” by the British health authorities, which means they keep a close eye on her but don’t worry too much.

BA.2 infections in Germany are also growing faster than those of BA.1 and delta, according to Dr Meera Chand, head of UKHSA’s covid-19 area.

Is BA.2 more contagious?

• Ómicron: 5 good news to end the year

Where is the BA.2 sublineage spreading?

Since November, 40 countries have added thousands of BA.2 sequences to the database.

According to the WHO, the subvariant is already becoming dominant in the Philippines, Nepal, Qatar, India, and Denmark. In some places, your growth has been abrupt.

India is another country where BA.2 is rapidly replacing the delta and omicron variant BA.1, according to molecular biologist Bijaya Dhak.

• Ómicron: 5 good news to end the year

The Philippines Department of Health (DOH) said the BA.2 sublineage was now prevalent in samples it received in late January.

And in England, more than 1,000 confirmed cases of BA.2 have been identified, according to the UK Health Security Agency (UKHSA).

It has been designated as a “variant under investigation” by the British health authorities, which means they keep a close eye on her but don’t worry too much.

BA.2 infections in Germany are also growing faster than those of BA.1 and delta, according to Dr Meera Chand, head of UKHSA’s covid-19 area.

Is BA.2 more contagious?

A study of 8,500 households and 18,000 people by the Danish ISS found the BA.2 subvariant to be “substantially” more transmissible than BA.1.

The BA.2 turned out more efficient at infecting vaccinated people and with a third booster dose than earlier variants, according to the study, although vaccinated people were less likely to transmit the virus.

While a UK study also found that BA.2 was more contagious compared to BA.1.

But a preliminary evaluation found no evidence that the vaccines were less effective against symptomatic disease for any of the subvariants.

Is the BA.2 subvariant more dangerous?

There are no data to suggest that BA.2 causes more severe disease than previous omicron subvariants.

“Looking at other countries where BA.2 is now outpacing (BA.1), we are not seeing larger increases in hospitalizations than expected,” Boris Pavlin of the WHO Covid-19 Response Team said on Tuesday. .

He also said that even if BA.2 replaces BA.1, this may have little effect on the trajectory of the pandemic and how people are treated.

“Its impact is unlikely to be substantial, although more data is needed,” he said. Pavlin.

As with previous variants, experts believe the vaccines will remain highly effective in preventing severe illness, hospitalizations, and death.

“Vaccination profoundly protects against serious disease, including omicron,” Pavlin explained.

“So far, there is not enough evidence to determine whether BA.2 causes more severe disease than omicron BA.1, but data is limited and UKHSA is continuing to investigate,” Chand said.

“We must remain vigilant and give ourselves the vaccines. We should all continue to get tested regularly with lateral flow devices and get a CRP test if symptoms develop.”