Covid mutant strain XE: Why Health experts not alarmed by new recombinant variant?
Mumbai, Apr 7: Health experts on Wednesday sought to downplay apprehensions centred around XE, a new coronavirus variant deemed more transmissible, and said despite being around since January, the strain has not propelled a surge in cases like Omicron, but advised strict adherence to COVID-19-appropriate behaviour.
The Brihanmumbai Municipal Corporation (BMC) on Wednesday said a woman who had arrived here from South Africa in February and tested positive for COVID-19 was found infected with the XE variant, which was first detected in the UK.
This was the first XE case in Mumbai. However, official sources in New Delhi clarified, "Present evidence do not yet indicate that it is a case of XE variant."
According to the Maharashtra health department, the XE variant was found in the 50-year-old woman, a South African national, who came here on February 10 and was tested on February 27 for COVID-19 with her test returning a positive result. Her lab sample was referred to Kasturba Hospital Central laboratory for genome sequencing.
"It has been found to be a new XE variant in initial sequencing. Though GISAID also confirmed it, INSACOG (Indian SARS-CoV-2 Genomics Consortium) has decided to go for another round of genomic sequencing at a national laboratory for sure confirmation of XE variant," the department said.
The woman was asymptomatic and found to be RT-PCR negative on repeat testing, the health department added.
Rakesh Mishra, Director of the Tata Institute of Genetics and Society, Bengaluru, said the XE variant is a recombinant of BA.1 and BA.2, the sub-lineages of SARS-CoV-2, the virus which causes COVID-19. In addition to those, it has three other mutations which were not there in Omicron or BA.1 or BA.2. "That is why it is called XE. It will now be a variant," he told PTI.
Senior epidemiologist Dr Raman Gangakhedekar, former head scientist of the Epidemiology and Communicable Diseases Division at the Indian Council of Medical Research (ICMR), said when a recombinant occurs, it tends to last for a lesser time. "Recombinant events are chance events because two different types of viruses are in the body and they tend to develop a recombinant new virus," Gangakhedekar said. He said the virus fitness does not increase by a recombinant event. It is unlikely to be stable as recombinants are rare events.
The state health department said the XE variant is a combination of BA.1 and BA.2 strains of Omicron and found to be responsible for enhanced viral transmission. Asked about its severity and transmissibility, Mishra said as far as the infectivity data is concerned, XE is 10 per cent more infectious than Omicron. This is based on the UK data, he said. "There is no information whether the clinical symptoms are worse, or whether its immune escape is more. Data is not available for the same," Mishra noted.
"The general perception is that this was the known (variant) since the middle of January and now we are two-and-a-half months past that. Not many cases of this variant are seen. The UK has some 600 cases. This means that if it was going to be dangerous, more infectious, by now we would have seen it everywhere," Mishra said.
The director of the Tata Institute of Genetics and Society said Omicron appeared in November (in South Africa) and it was all over the world in 4 to 5 weeks and replaced Delta (which caused the second wave in April-May last year), but XE has not done that.
"I don't think XE is of any concern to us. It doesn't look like we have to worry about it. But we have to exercise caution and follow COVID-19 protocols," Mishra said. Gangakhedekar said he doubted that it is transmissible like BA.2.
"Frequent changes in genomic structure are part of the natural life course of viruses and there is no need to worry but everyone should opt for appropriate precaution. There is no strong epidemiological evidence that the transmissibility is very high because had that been the cases, we would have seen a surge in the cases. But this must be tracked," the senior epidemiologist said.
Anurag Agrawal, Dean, Biosciences and Health Research at the Ashoka University, said there is "no critical global signal of concern as of now" with regards to XE. The World Health Organisation on April 2 said XE appears to be more transmissible than previous strains of the coronavirus, and stressed that COVID-19 remains a public health emergency of international concern and warning that it is too early to reduce the quality of surveillance.
The WHO said in its latest update that the XE recombinant (BA.1-BA.2) was first detected in the UK on January 19 and more than 600 sequences have been reported and confirmed since then. Early-day estimates indicate a community growth rate advantage of 10 per cent as compared to BA.2. However, this finding requires further confirmation, it said.