Two more fliers who arrived from Dubai between February 23 and March 4 were detected with UK strain of the mutated SARS-CoV-2 virus, that causes Covid-19, on Sunday.

The number of people reaching Calcutta with mutant strains of the coronavirus now stands at six, health department officials said.

Earlier four of them had tested positive for the mutant strains of the coronavirus, including one with the South African-strain, and the rest with the UK-strain.

Among the three fliers tested positive for the UK strain one was admitted to Infectious Diseases (ID) Hospital in Beleghata on Saturday. The state government from Monday will start tracing other passengers and crew members of the flights on which these people had travelled. The family members of those who have tested positive have been asked to undergo RT-PCR test for Covid-19.

On Sunday, the remaining fliers were admitted to the same hospital in a special ward, which has been set up for such patients. Till late evening the condition of all the six was stable, doctors said.

Health department officials said these passengers had flown in from Dubai between February 23 and March 4 and had tested negative during the mandatory RT-PCR tests ahead of boarding their flights to Calcutta. All of them worked as labourers in Dubai except one, who works at a hotel. That man in his late 40s hails from South 24-Parganas. He had arrived on March 4.

The remaining fliers, in their late 30s and early 40s, are from of Nadia and Malda. The passenger who has tested positive for the South African-strain — the first such case in Bengal — is from Ratua in Malda.

After arriving in Calcutta these fliers had undergone RT-PCR tests along with other passengers and their samples were sent to the National Institute of Biomedical Genomics in Kalyani. The confirmation about the presence of the mutant variety of the SARS-CoV-2 virus reached two days back spurring the health department to initiate a follow up action, including bringing these fliers to the city and admitting them at the Beleghata hospital.

“No decision has yet been taken about restricting flights from Dubai. We have had a case of a passenger testing positive for the UK-strain earlier too. There is no need to panic,” Narayan Swaroop Nigam, health secretary, told Metro.

“We will contact the airlines on Monday and collect a list of passengers and members of the crew for each of the flights that these fliers had boarded,” said Ajay Chakrobarty, state’s director of health services. “Our team members will call them to ask if they were facing any health complications since their arrival.”

Fliers landing in Calcutta and have not tested positive during the mandatory RT-PCR test would have to stay in home isolation for 14 days according to a directive drawn up by the state government. During this period if any of them develops complications, including shortness of breath, they would have to inform the health department.

A medical team from the civic body would keep in touch with the flier and monitor his health condition, the directive states.

Senior health department officials admitted this process of monitoring is often fraught with slackness leaving it mostly on the fliers to inform about their health condition to the health department. Most don’t.

The daily bulletin published by the state health department showed the state reported 259 new cases on Saturday and fresh 255 cases on Friday. A week ago the numbers were lesser. The state had reported 210 fresh cases on February 27 and 216 new cases on February 26.

Calcutta reported 83 new cases on Saturday and 78 new cases on Friday. The city had reported 69 cases on February 27 and 72 cases on February 26.

At the Beleghata hospital, the fliers have been admitted to the High Dependency Unit of a special ward that has been created and a team of doctors has been set up for round the clock monitoring. None of them showed signs of falling levels of oxygen in their blood, doctors said.