A man, who had returned to Kolkata from Ireland last week, tested positive for Covid-19 following which he was hospitalised on Tuesday, a health department official said.
The department is waiting for the genome sequencing report of the 27-year-old man to check if he was afflicted with the Omicron variant of coronavirus, he added.
"The man who has been working in Dublin, Ireland, for the last five years, arrived in the city flying from Manchester via Abu Dhabi and New Delhi. He was admitted to a hospital on Tuesday morning," the official said.
His genome sequencing report from the National Institute of Biomedical Genomics (NIBMG) at Kalyani is expected within 72 hours, he added.
"He had tested negative for Covid on December 16 at a lab at Dublin, a day before his flight, and then again upon arrival at Delhi airport. He reached Kolkata on December 18 evening and went straight to his home.
"From Monday morning, however, he started running a high-grade fever (103 degrees Fahrenheit or above) along with body ache, malaise and headache, after which a test showed that he was Covid positive," the official said.
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The patient has said he had been indoors since his arrival in Kolkata, as per the guideline for international travellers which says they have to remain in home isolation for eight days, and venture out only after testing negative through an RT-PCR test.
Meanwhile, on Tuesday, West Bengal's Covid-19 death toll rose to 19,688 after 12 more fatalities were reported in the last 24 hours, a health department bulletin said.
Three deaths each were registered in Kolkata, North 24 Parganas and Nadia districts while Hooghly and Birbhum districts recorded two and one fatalities respectively.
Altogether 440 new cases pushed the state's Covid tally to 16,27,930, the bulletin stated.
In the last 24 hours, 451 patients recovered from the disease taking the total number of cured people to 16,00,791. The discharge rate remained at 98.33 per cent.
The number of active cases is 7,451.
A total of 32,871 samples were tested for Covid-19 in West Bengal on Tuesday, taking the total number of such clinical examinations to 2,10,59,843.