Updated: December 28, 2021 11:45:48 am
As many as 52 of the 63 cases of infection with the Omicron variant of the coronavirus detected in Delhi on Monday are in individuals who have reported no history of international travel or contact with an international traveller, officials from the Delhi government told The Indian Express.
“District surveillance teams will now trace these cases and re-confirm whether they have any history of travel or history of coming in contact with any foreign travellers,” a senior health department official said.
“We need to be sure. We will come to know in a day,” the official said.
The Indian Express had reported last week that all but one of the 34 Omicron cases treated at Delhi government’s Lok Nayak hospital were fully vaccinated. Also, the bulk of these cases — 31 out of 34 — had a history of foreign travel or contact.
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The upending of this ratio in cases that were detected on Monday — only 11 out of 63 have a known history of foreign travel or contact — could potentially indicate a wider community spread of the new variant.
The highly transmissible Omicron variant is known to evade existing immunity from vaccination, leading to more breakthrough infections, though not necessarily to a higher incidence of severe Covid-19 disease. A total 142 cases of Omicron infection have been detected in Delhi so far.
“For nearly four months now, ever since the number of daily cases fell to manageable levels, we have been sequencing all positive samples with a CT value of less than 25. The cases of Omicron were detected in this process of genome sequencing,” the health department official said.
Sequencing maps out the entire viral genome and ascribes a family to it. The positive samples from Delhi are sequenced at the National Centre for Disease Control, and two state laboratories at the Institute of Liver and Biliary Sciences and Lok Nayak hospital.
CT value or cycle threshold value is the number of amplification cycles that a patient sample has to go through in an RT-PCR test to detect the virus. The lower the CT value, the higher is the viral load. The threshold of CT value less than 25 ensures that the sample is good enough to be fully sequenced.
Another official said, “Initially, all cases of Omicron were being detected only in international travellers; slowly, during the last week, we are reporting cases from the community too. Today, 52 cases were detected in the general samples.”
The official recalled a specific case in which an individual who was tested frequently returned a positive result. “He had no symptoms at all. There was no history of travel. But when the sequencing result came back, he was found to have the Omicron variant,” the official said.
The patient was admitted to Lok Nayak hospital, which is the biggest centre designated for the treatment of Omicron cases, the official said.
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