The state health department has prepared a list of least 442 people who have come in close contact with the 66-year-old Calcuttan who tested positive for Covid-19 on Wednesday.

The man, who is in a critical condition and is being treated at a private hospital off EM Bypass, does not have any travel history abroad but recently came in contact with people from other states and abroad.

He was in his brother-in-law’s house in East Midnapore’s Egra from March 12 to 23 to attend a wedding and went on a trip to Digha with his 61-year-old wife in between. He returned to Calcutta on March 23 and was admitted to the hospital the same day.

A health department official said people from other states, a person from Singapore and a Calcuttan who recently returned from the US attended the wedding.

All 442 “contacts” have to stay in quarantine — at home or a government-run facility — depending on the degree of exposure. A health department official said more people might be included in the list.

The 66-year-old, Calcutta’s 10th Covid-19 patient, has the longest list of contacts compared with other confirmed coronavirus cases in the state.

The enormity of the challenge to ensure that none of the contacts spreads the virus if he or she has already contracted it has left the health department worried.

“We have to get many of the contacts tested. It’s a mammoth task,” a health department official said.

The revised guidelines of the Indian Council of Medical Research issued on March 17 said all physical and high-risk contacts of a positive person must undergo tests even if they do not show any symptom. Earlier, the ICMR’s guidelines said contacts needed to be tested only if they showed symptoms.

The 66-year-old man — a resident Nayabad, on the southeastern fringes of Calcutta — has been running a temperature since March 14, an official of the hospital where he is being treated said.

Another official of the hospital said on Thursday evening that his condition “was very critical” and he was on ventilator support.

“He visited the hospital on March 23 and was admitted the same day after doctors became suspicious that he could be a Covid-19 patient,” the official said.

“Our thermal scanner detected he was running a temperature when he visited the hospital. We immediately sent him to a room where people with fever are being sent to segregate them from other patients.”

His samples were sent for tests on Tuesday and the first results were positive. A second round of tests was conducted on Wednesday and the results were positive again.

“We have shifted him to the isolation facility that has been created for Covid-19 patients. We have been treating him as a Covid-19 patient since the first results came. Now, he is the only patient in the isolation facility in our hospital,” the official said.

The man’s wife and son were on home quarantine initially on advice of doctors of the hospital and were later admitted to the isolation ward of the Infectious Diseases and Beleghata General Hospital.

An official in the East Midnapore district administration said the man and his wife visited Digha on March 17 and spent a night at an old Digha hotel before returning to Egra. Two doctors in Egra examined him after he took ill.

As many as 1,000 people in East Midnapore will have to be sent to quarantine, the official said.

Twelve people, including the man’s brother-in-law and his family members and the two doctors from Egra, have been sent to an isolation facility at Egra Super-speciality Hospital. The employees of the Digha hotel, the staff of the caterer who served food at the wedding and many residents, too, have been quarantined.

“The administration is appealing to the people of Egra over the public address system to identify those who had attended the wedding,” said Nitai Mondal, chief medical officer (health), East Midnapore.

“The man (the Covid-19 patient) arrived in Egra on March 12. He visited Digha with his wife on March 17. We have identified the hotel,” Mondal said.

The man whose wedding the patient attended said guests from Delhi, Hyderabad, Gurugram, Agra and Singapore had attended the wedding. “I have checked with all of them. None has taken ill or is showing symptoms,” he said over the phone from the quarantine facility where he and his family members have been taken.