The city's first suspected Omicron patient was quarantined on Friday at a private hospital after testing positive for Covid-19 upon arrival from UK.

Health department sources said the specimen for genome sequencing had been sent and that the patient was in a stable condition.

The Omicron variant of Covid first flagged by South Africa on November 25 was assessed by the World Health Organisation on Sunday as a global high risk.

Preliminary data indicates the infection rate of Omicron variant is higher than the other variants and could breach the immune system, bypassing previous infection and vaccination.

The first two cases of Omicron were reported from Karnataka earlier this month. Since then, six members of a family in Pune and nine others from the same family in Jaipur who had travelled from Nigeria had also tested positive for the variant. Another man who arrived from Finland to Delhi had also tested positive with the new variant.

Lav Agarwal, the joint secretary in the Union health ministry said on Friday, the total number of confirmed Omicron variant Covid patients in the country was 25.

The Calcutta patient was initially kept at Beliaghata’s Infectious Diseases hospital and later moved to a private facility on the family’s insistence.

Till December 9, 567 new Covid cases and seven deaths were reported from Bengal, according to the figures released by the state health department.

Genome sequencing is crucial for conclusive evidence for the Omicron variant, which can also be detected by the conventional RTPCR test route.

The polymerase chain reaction (PCR) test for Covid-19 is a molecular test that analyzes the upper respiratory specimen, looking for genetic material (ribonucleic acid or RNA) of SARS-CoV-2, the virus that causes Covid-19.

Patients who test negative for spike protein, yet found to be Covid positive is an indication of the presence of the Omicron variant.