COVID-19 ‘double mutant’ variant directly colonizes lungs, avoids RT-PCR: Experts

The so-called ‘Bengal variant’ of COVID-19 appears to have reached a plateau, say medical experts

The ‘double mutant’ Indian variant of SARS-CoV-2, B.1.617, indeed avoids reverse transcriptase polymerase chain reaction, or RT-PCR testing, doctors have admitted.

Another close variant, B.1.618, was first isolated from West Bengal in October 2020; also adds to the risk. However, the scientists studying it have confirmed that its growth appears to have reached a plateau ”.

Many patients in Delhi and Mumbai as well as Kolkata recently complained that RT-PCR testing, the gold standard for identifying a new coronary virus disease (COVID-19) infection, had returned negative reports.

These patients then had to undergo further tests to detect the infection as COVID-19-like symptoms continued to ravage them.

“It’s a fact. My father-in-law, who had an RT-PCR test, was found to be negative but found positive in HRCT (high-resolution computed tomography) as his symptoms continued, ”a doctor from COVID-19 unit of Beliaghata ID Hospital in Kolkata told this reporter.

“About 5 per cent of patients who come to us show such a trend and we have to rely on HRCT and bronchoscopy to confirm the presence of the virus and start treatment,” the doctor added.

Ajay Sarkar, a critical care specialist in charge of the COVID-19 unit at Kolkata Peer Hospital, said such cases were smaller in the first wave of the disease last year, but have increased this time.

RT-PCR is a method used to detect the presence of a particular genetic material in any pathogen, including a virus.

Public health and genetic experts echoed the clinical finding about the RT-PCR test.

“The conventional SARS-CoV-2 strain usually colonizes the nasopharyngeal region where the body’s immune system counteracts it and prevents it from directly accessing the lungs,” said Anirban Dolui, a public health specialist who is affiliated with the West Bengal government.

However, the double mutant variant was thought to bypass the nasopharyngeal region and directly colonize the lungs, he added.

That may be the reason why the viral load in the sample drawn is not from the nasopharyngeal region, leading to negative recording of the patient, he explained.

“It is a fact that the double mutant appears to bypass the patient’s nasopharyngeal region, as it escapes the body’s immune system,” confirmed Dhrubojyoti Chatterjee, vice-chancellor of Sister Nivedita Kolkata University and molecular biologist.

Earlier, various logistical and technical factors such as improper sampling, improper transportation and delay in testing along with the use of less sensitive reactors and technical incompetence had been responsible for COVID-19 positive patients reported as negative, said Krishnajyoti Goswami, a scientist biochemical. .

Mutants add to the anxiety

Chatterjee pointed out that while the role of the double mutant strain was not yet fully clear in West Bengal, Maharashtra and Delhi appeared to be having a serious impact.

B.1.617, the double mutant variant, carries two mutations, L452R and E484Q, at the same time.

Vinod Scaria, a scientist at the Scientific and Industrial Research Council-Institute for Integrative Genomics and Biology, tweeted:

B.1.618, a variant first discovered in West Bengal last October and hence known as the ‘Bengal variant’, has been growing significantly in recent months in the state of West Bengal, India … and along with B.1.617, it forms the main SARS-CoV-2 dynasty in the state of West Bengal.

Experts have pointed out that B.1.618 has four mutations to the spike protein that are associated with increased infectivity and an innate escape response.

However, there is still no conclusive evidence that the strain plays any part in the current increase in COVID-19 cases in West Bengal where the number of people affected each day has increased almost five times in the past two weeks.

“B.1.618 peaked during January but now appears to have reached a plateau; it’s just a variation of interest (VOI) for us at the moment, ”Soumitra Das, director of the National Institute of Biomedical Genomics at Kalyani near Kolkata, told this reporter.

However, Das explained that while the double mutant variant was also VOI, its circulation was still fairly high in some areas of Bengal such as Kolkata, South 24 Parganas, North 24 Parganas and Howrah.

West Bengal April 21 for the first time added more than 10,000 new cases even as the second wave raged throughout the country.