Revelations that a group under coronavirus watch had travelled on two popular trains in Bengal and reportedly moved about freely before they tested positive have prompted the Nadia district administration to issue an appeal to the people.

The administration has requested those who might have come in contact with five now-confirmed patients (four who came from Delhi and a relative who was in Nadia) to identify themselves so that they can be brought under medical management, and the possibility of the spread of the coronavirus can be minimised.

Till Saturday evening, none had responded to the appeal, which a source in the district administration said was “very worrying”.

The four Covid-19 patients, who had jumped home quarantine in Delhi and tested positive in Tehatta, Nadia, on Friday, a relative in Tehatta who also tested positive and eight contacts were admitted to hospital in Calcutta on Saturday.

The five patients were brought to Calcutta and admitted to the Infectious Diseases and Beleghata General Hospital, health department officials said.

Eight of their contacts from Tehatta too were admitted to a government hospital in south Calcutta, the officials added. They will be tested for the virus.

“None of the eight have any symptoms of Covid-19 but we have kept them in hospital quarantine as they are high-risk contacts of the five patients. They had attended a family event in Tehatta where the five patients were present,” a health official said.

A “high-risk contact” is one who has come in direct contact, without protection, with someone who has tested positive. The revised testing guidelines of the Indian Council of Medical Research make it mandatory to test asymptomatic high-risk contacts between 5 and 14 days of their having come in contact with the patients.

The eight contacts had already been in home quarantine for about a week following advice from health officials in Nadia. The advice was given after one of the five who later tested positive visited a fever clinic at a government hospital in Tehatta and the doctors became suspicious after examining her.

On questioning her, the doctors learnt that she and a few others in the family had come in contact with a male relative in Delhi who later tested positive for Covid-19 in the national capital.

The family members had been advised home quarantine in Delhi but four of them ignored the advice and travelled to Nadia to attend the family event.

Sources in the Nadia administration said that their information was that the woman in her late twenties “was medically examined and put under quarantine at the RM Lohia hospital on March 17 but she left on March 18”. Health department sources in Calcutta said they were unable to confirm this.

A source close to Mamata Banerjee said the chief minister was livid with the “irresponsible behaviour” of the woman.

“The government is trying its best to keep people of Bengal safe.… But such irresponsible act by those returning from abroad or from other states are putting all of us in great risk. This has to stop and people have to co-operate with the government,” said the source.

According to the source, the chief minister thinks that the bigger challenge, however, was to identify the people, who could have come in contact with these five people.

Health officials said these four took the Rajdhani Express to Calcutta and then one of the Lalgola Passenger trains to Bethuadahari, Nadia, on March 20. The fifth patient, an 11-year-old boy, was in Nadia.

From Bethuadahari, the four had taken an auto-rickshaw to Barnia in Tehatta. It’s unlikely that the auto driver can be traced, health officials said.

Health department officials were on Saturday evening waiting for a list of the patients’ contacts on the Rajdhani, which left Delhi on March 19 and arrived in Sealdah on March 20.

“We will be able to get in touch with the potential Rajdhani contacts from the reservation details. But there’s no way we can find out who had boarded the passenger train the four took from Calcutta to Bethuadahari. That’s the worrying part,” a health department official said.

“We will ask the patients’ Rajdhani co-passengers to stay in home quarantine for 14 days. But the patients’ contacts on the Lalgola Passenger may end up spreading the virus if they have contracted it.”

The district administration has launched an extensive campaign — using microphones in the vicinity of Barnia and adjacent villages — urging people to voluntarily disclose if they had come in contact with the five persons.

Tehatta sub-divisional officer Aneesh Dasgupta said that a disaster was waiting to happen if they failed to identify those who came in contact with the five persons.

“We are afraid as we don’t have any clear idea about the number of persons who came in contact with the affected persons. We have heard that they mingled with people, did shopping and went around visiting relatives. So there is every possibility of large-scale transmission of the disease,” Dasgupta said.

The district administration also decided to launch health scanning of people in the area to zero in on those who could have come in contact with the coronavirus-affected people.

“We have alerted all village level health workers and doctors closely to scan local people and identify those with suspected symptoms.… This is the only way left for us now,” Dasgupta added.