Covid-19: Highly transmittable Delta strain found in 61% PGIMER samples

The highly transmittable mutant of coronavirus, Delta strain, was found highly active during the second wave of the pandemic in Chandigarh, as it was detected in 61% of the samples sent by the Post Graduate Institute of Medical Education and Research (PGIMER) for genome sequencing.

To study the change in the circulating strain and to check the prevalence of mutant strains in Chandigarh residents during the second wave, the PGIMER had sent 25 stored samples of Covid-19 patients for genome sequencing to the central government’s epidemiology unit — National Centre for Disease Control (NCDC), New Delhi. Genome sequencing attempts to draw out the complete genetics of the viruses.

The samples were of patients who were tested positive from May 5 to 24 — a period that saw the second wave peaking in Chandigarh with 12,758 cases and 191 deaths. The 25 samples were selected randomly and included those of a few critical patients, two children, and five patients who had already died. As many as 23 were of Chandigarh residents.

The genome sequencing results received on Sunday revealed that 61% of them were positive for the Delta strain and 30% for the UK or Alpha strain. However, the UK strain was found in samples of 80% of the deceased patients (four out of five). Meanwhile, no case of the Delta plus variant has been reported in Chandigarh so far.

“In two samples, sequencing could not be performed due to low content of genomic material. The Delta strain, which is highly transmittable, was the main circulating strain in Chandigarh residents,” said professor Jagat Ram, director, PGIMER.

The B.1.617.2, known as Delta variant, is the sub-lineage of a double mutant of coronavirus (B.1.617), which was first detected in India earlier this year. WHO has categorised it as a variant of concern and said that it can significantly increase the transmissibility of viruses. The Delta plus variant is its mutated version.

The UK or Alpha variant (also known as B.1.1.7) was first detected in Britain, and has spread to more than 50 countries with more than 2 lakh cases identified. It is believed to be 70% more transmittable and dangerous than Covid-19.

Earlier in May, 39% of the 23 samples sent by the PGIMER were found positive for the UK strain while double mutant (B.1.617) was confirmed in 22% samples. The institute will send 50 more samples for genome sequencing this week. “These will include samples of severely ill patients and also of those who have died due to the infection,” said virologist Mini P Singh.