Home/ News / India/  How genome sequencing can confirm presence of Omicron variant, expert explains

With the World Health Organisation (WHO) categorising the newly discovered Covid-19 Omicron strain as a “variant of concern", India is on a high alert to prevent it from wreaking havoc in the country. 

The central government has advised states and union territories to ramp up testing and undertake effective surveillance of international passengers while extending the nationwide Covid-19 containment measures till 31 December.

While no cases of Omicron have been reported so far in India, more than a dozen countries have detected the variant. 

In view of this, Dr Naveen Dang, the director of Dr Dangs Lab, has explained how Omicron is detected in genome sequencing and how is it different from other variants of concern.

“Different variants mean that there have been mutations in one or more of the genes. The previous mutants may also have a couple of mutations, but in Omicron we have a very large number of mutations that have occurred, nearly about 50 mutations, and out of these nearly 30 are in the spike protein," Dang was quoted as saying by news agency ANI.

"That is what makes it different from the other mutations of the Covid virus which we have experienced in the last two years," he added. 

The doctor went on to say that gene sequencing, depending on the suspected cases and the missing S-gene, is one of the indicators for detection and ultimate diagnosis for the potentially more infectious Omicron.

One of the S gene targets is not detected due to mutations and this termed the S gene dropout or S gene target failure, is a marker to identify the Omicron variant, says Dang.

“The S-Gene dropout, or as we say the S-Gene target failure or SGTF, is one of the proxy indicators to (ascertain) whether or not it is the Omicron variant. But this is not necessarily so as the ultimate diagnostic tool is distinct for gene mutation," said the doctor

“So, if there is a patient who is suspected (to be infected) with Omicron, the ultimate diagnosis relies on testing but testing for the mutations that are called gene sequencing," he added. 

Dang further explained the process of detecting whether the S-gene has gone missing.

The mutations in the latest variant have occurred in the S gene. The common RT-PCR kits being used will be able to identify positive or negative, but will not be able to identify if the positive result is due to the mutation in the S gene

“When we are doing tests, most of them target a large number of genes. Now usually tests in India test the E, N and Rd Rp genes. Even if one of these genes (identifies as) positive, we can (identify) they tested positive for Covid-19,"  said Dang. 

“However, most of the tests in India are not (testing) the S-gene because there was no kind of requirement for it. But if we have a test in which you have multiple genes, and one of the genes included in the SG and if the test shows positive for all the genes but negative for S-gene, we can say that this is an S-gene dropout or S-gene failure target failure," he added. 

The doctor said that in such a situation, by proxy we can say that this is Omicron. "We send such samples for gene sequencing studies. So once that is done only then only it can confirm whether it is the variant or not."

According to the expert, since Omicron was very recently detected, there is very little data on its transmission and spread and scientific data is still being collected and is really early to say about how contagious the strain could be.

"We do not know how severe the cases are going to be. As you know very well that this virus was first identified and spoken about on 26 November, is not even a week back. So it is too early to comment how severe the infection is going to be. Different kinds of data are coming in and everybody is working extremely hard to find out where we are and where we're going to go," Dang said.

As a precautionary measure, Dang emphasised on maximum vaccinations and if required, an additional booster dose to fight against Covid-19. He also strongly advocated following Covid appropriate behaviour.

"Unfortunately, a large number of us have lowered our guards. Those guards should be back in place. The promotion should be more stringent now. And of course, most important is that you must make vaccinate as many of our population as possible by both the doses and when required. Even a booster may be in," Dang said. 

With inputs from agencies. 

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Updated: 01 Dec 2021, 09:17 PM IST
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