Genome sequencing: 64% of strains belong to Omicron sub-lineage

KOLKATA: Genome sequencing carried out by the School of Tropical Medicine on 564 odd Covid samples collected from various parts of the state, reveals that 64 per cent of the virus strains belong to Omicron sub-lineage while a substantial 36 per cent of strains could not be identified.

According to the Health department data, around 11 Omicron sub-lineages were detected during Genome sequencing of samples in Bengal in June. No Delta variant has been found in the current situation. It may be mentioned here that the Delta variant triggered a second wave of Covid across the country.

Dr G Mukherjee, a senior pathologist from the state said that strains are mutating from one variant to another. Delta created havoc in Bengal and the rest of the country during the second wave while the third wave was mostly caused by the Omicron variant. Bengal now has been witnessing a surge in the past few weeks but this time nearly around 36 per cent of the strains collected from samples during genome sequencing could not be identified. It also suggested that the remaining 64 per cent of the strains belong to Omicron sub-lineage. This also suggests that Omicron sub-lineages are still predominant across the state, Dr Mukherjee further added.

The state Health department had already directed all the pathological laboratories to focus on CT Value of Covid positive samples and if the CT Value of a sample goes below 30, that particular sample must be sent for genome sequencing. It aims to detect whether any new Covid variant is prevalent in Bengal.

The department had taken the step after the daily infection rose in the state. The Indian Council of Medical Research (ICMR) suggested that if the CT Value in a report is 35 or more it can be considered as a negative report. It could also signify that the virus is in its initial stages and replication in the body has just started.

Fifth sentinel survey carried out by the health department reveals that the number of asymptomatic Covid patients far outweighs the number of symptomatic patients this time. Health department has also identified 11 places across Bengal where Covid infection rate is comparatively higher and these areas have been included under red zone while 8 districts have been demarcated as yellow zone where the infection is comparatively low.