An international flier, who reached the city recently, has been found positive for the South African-strain of the coronavirus and three others have tested positive for the UK-strain, senior officials of the health department said on Saturday.

The confirmation about the presence of these strains reached the health department on Friday, days after the samples were sent to the National Institute of Biomedical Genomics in Kalyani. Officials said these passengers had flown into Calcutta in February end and had undergone the mandatory RT-PCR test for Covid-19.

Till Saturday evening, one of the three passengers with the UK-strain of the SARS-CoV-2 virus has been admitted to the Infectious Diseases (ID) Hospital in Beleghata, health department officials said.

“One of the four passengers have been found to be positive for the South African-strain and three others have tested positive for the UK-strain of the coronavirus...,” Ajay Chakraborty, director of health services, told Metro.

The person who has been admitted to ID Hospital is a resident of Nadia district and is 30-year-old. A team of Covid-19 doctors has been engaged to monitor the patient’s condition round the clock. His contacts back in Kalyani have been asked remain in isolation and their samples have been sent for tests.

“The patient is doing fine,” said a senior doctor of the hospital.

In January, a 38-year-old UK-based professional, who flew into Calcutta, had tested positive for the UK-strain.

On Saturday, immediately after the results of three others reached Swasthya Bhavan, a team of officials called up the family members of these fliers and asked them to go into isolation. The fliers have been asked to regularly check the saturation level of oxygen in their blood till the time they are admitted to the ID Hospital.

A report with details of these passengers was sent to the Union ministry of health on Saturday along with measures that the state government has taken in handling them.

“So far we have found that all the four, tested positive with mutant strains of the coronavirus, are asymptomatic,” said a senior health department official. “Specific protocols about how to handle such patients and what needs to be done after they have been tested positive for mutant strains of the coronavirus has been developed. There is no reason to get unnecessarily alarmed.”