Omicron sub-variant BA.5 continues to be the dominant variant in circulation in Tamil Nadu. But BA.2.75, a newer sub-lineage of Omicron that was detected in less than 5% of the samples analysed in July, showed an increased presence in August with 19.1% of the samples testing positive for the sub-variant, latest Whole Genome Sequencing (WGS) has found.
The Directorate of Public Health and Preventive Medicine’s WGS-SARS-CoV-2 variants of concern reported that the State, as of September 11, showed that the Omicron sub-variant BA.5 was the dominant variant in circulation in June, July and August. From being detected in 47% samples in June, it was found in 77.9% samples sent for genomic analysis in July, and in 66.3% samples in August.
The newer Omicron sub-lineage BA.2.75 was detected in more samples in August when compared to July. In July, it was detected in 4.2% of the 1,650 samples sequenced and in 19.1% of the 282 samples sequenced in August.
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Other sub-variants
The other sub-variants found in the August analysis included BA.2 (4.6% of samples) and BA.2.74 (2.1%).
Director of Public Health and Preventive Medicine T.S. Selvavinayagam said samples lifted from eight places and testing positive for COVID-19 such as unusual presentation, child mortality, death without co-morbidities, clusters, same source of infection in addition to two percent international travellers, continue to be sent for genomic sequencing in the State.
“Tamil Nadu is the only State in the country to have the capacity to do whole genome sequencing on our own,” he said, adding: “The ratio of BA.2.75 sub-variant among the samples sequenced has increased. We are trying to link it with the present clinical situation in the State. Though we are noticing symptomatic COVID-19 cases in two to three districts, we are not very sure. The epidemiological behaviour of COVID-19 remains the same.”
He said that it was important to continue adherence to COVID-19-appropriate behaviour and getting vaccinated.
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