Omicron driving Covid surge in Karnataka, say experts

The number of known Omicron cases may be relatively small in the state, but there is little doubt that the new variant is driving the fresh surge, experts said.

As of Tuesday, Karnataka had 226 confirmed Omicron cases even though it has recorded 21,102 Covid-19 cases since December 2, when the first two Omicron cases in the state were made public.

“There is little doubt in my mind that Omicron is driving the current surge in cases. Based on the epidemiological pattern, four out of five new cases being found in the country are due to Omicron,” virologist Dr T Jacob John told DH.

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State Health Commissioner D Randeep concurred that Omicron cases have started to comprise a large chunk of cases from January onward. “Genomic sampling will increasingly show this in the days to come,” he said.

An analysis by DH of existing sequencing results in the state for the last one month had found that while the Delta sub-lineages are continuing to play a role in the outbreak, showing a 141% increase in the last 30 days, Omicron cases have bolted upwards at a rate of over 11,000%.

A national-level genomic expert in government, who did not want to be named, also told DH that "in Delhi and in Mumbai which has sequenced, (Omicron) has dominated and become a major proportion".

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While in Karnataka too, the scale of Omicron’s presence in this new outbreak could be verified by genomic sequencing, ongoing lag in results means a genomic picture of the outbreak that is slightly outdated, officials said.

“There is a delay of 3 to 8 days before the sequencing result comes back. Furthermore, only about 1% of samples from positive cases are being sent for sequencing,” officials said, clarifying these limitations are due to the state’s capacity for sequencing having been reached.

Amid this handicap (which also extends to other states), experts noted that epidemiological patterns can help make a determination. “The current surge is marked by a higher test positivity rate, a higher R-value and a faster doubling period than can be caused by the Delta variant or its sub-lineages,” Dr John pointed out.

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When DH looked at the state’s Test Positivity Rate (TPR) in the first seven days of the Delta-driven second wave (from March 12 to 18), the rate was found to have risen by 40.7%. In the first seven days of this latest surge (from December 29 to January 4), the TPR rose from 0.52% to 2.60%.

A data expert formerly with Covid-19India.org said that while Bengaluru’s rate of increase is high compared to the second wave, it has not yet reached the scale of Delhi or Mumbai to offer conclusive confirmation that Omicron is responsible. “However, low testing in Bengaluru could be blamed for this,” he said.

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