Bengal has reported its first case of the mutant coronavirus that has been detected in the United Kingdom, a senior health official said on Wednesday.

The patient, the son of a senior official of the Calcutta Medical College and Hospital, tested positive for the mutant strain VUI-202012/01 following his return from London, the official added.

“The youth is undergoing treatment at the state-run hospital's super-specialty section. He is under observation. We have advised all those who have come in contact with him to isolate themselves,” he told PTI, adding that the mutant strain is believed to be more contagious than the existing one.

The youth had tested positive for Covid-19 10 days ago at the Netaji Subhas Chandra Bose International Airport, upon his return to Calcutta, the official said.

“Six others who had come in contact with the youth at the airport tested negative for the infection. As he had returned from the UK, we had sent his samples for genetic analysis as per the protocol set by the Centre,” he added.

“The new strain of the coronavirus was detected during his genetic analysis. We have sent the report to Delhi-based National Centre for Disease Control,” the official said.

Twenty cases of the mutant coronavirus strain have so far been reported across the country, of which eight were detected in Delhi and seven in Bengaluru.

The mutant strain VUI-202012/01 (the first Variant Under Investigation in December 2020) is defined by a set of 17 changes or mutations.

More than 40 countries including India have banned travel to and from the UK, a move several scientists said was necessary in view of the rapid spread of the VUI-202012/0, which was first detected on September 21.

Bengal on Tuesday logged 1,587 Covid-19 recoveries, 1,244 new cases and 30 deaths, including four from Calcutta, as the state recorded a drop in total active cases for the 64th successive day since Vijaya Dashami on October 26.

Active cases fell in these 64 days from 37,190 to 12,788, improving by nearly 66 per cent. In this period, Bengal recorded over 2.17 lakh recoveries and 1.95 lakh new cases.

The state now has a total of over 5.49 lakh Covid-19 cases, including 5.27 lakh recoveries and 9,655 deaths. The recovery rate has risen for 68 consecutive days, from the 87.44 per cent of October 22, to 95.92, short of the national rate by just 0.01 per cent now.