Corporation officials are going door to door to seek out people with symptoms of Covid-19.

Nearly 1 lakh homes in the city have been covered since the door-to-door surveillance began on Thursday, corporation officials said.

The first round of surveillance is expected to be wrapped up in about 20 days, followed by a second round.

Some officials are, however, worried about the 20-day gap between the two visits since the incubation period or the duration within which symptoms of Covid-19 emerge is 14 days. Shortage of manpower makes it impossible to increase the frequency of visits, they said.

The corporation team, will, however, not visit apartments. The civic body has requested the residents’ associations of gated communities to complete the survey on their behalf.

The surveillance work is being carried out by 600 honorary health workers engaged by the Calcutta Municipal Corporation’s (CMC) health department.

Each of the 144 wards in the city has four to five such health workers. “We have asked each honorary health worker to visit 50 homes a day. It is not possible for one person to cover more,” the official said.

The health workers have been asked to take down details of all residents of a home and also ask if they had any symptoms of Covid-19 — fever, dry cough or shortness of breath.

If a health worker comes across an individual suffering from fever or other Covid-19 symptoms, the surveillance in the immediate neighbourhood will be intensified and the focus will be on finding out if anyone else in the locality is suffering from fever or other symptoms.

“The time taken to complete the first round of home surveillance would vary. In a ward with fewer people and lesser expanse, it may be completed in eight to nine days. But in larger wards with more people, the first round may take 17-18 days or even more,” a doctor in charge of surveillance in a CMC borough said.

Several residents of Kasba and Behala told Metro civic officials had not yet visited their homes.

A public health specialist praised the initiative but added that health workers should communicate with all residents clearly on the first visit itself so that there is no need for a second visit. “While the effort to go to each home in Calcutta is a good one, why is the civic body even thinking about a second visit?” asked Shahid Jameel, the CEO of The Wellcome Trust-DBT India Alliance.

“The personnel visiting homes should speak a language people understand. They should be clearly instructed

to remain patient and answer all questions of the residents. The corporation must own people’s trust. It is then that people will themselves report in case they develop any

symptom. The communication from the civic body should make it clear where to inform and when,” Jameel said.

India Alliance works in biomedical, clinical and public health research and is funded by the Centre’s department of biotechnology and the Wellcome Trust of the UK.

The civic body’s health department also has 3,000 field workers who are part of the efforts to prevent vector-borne diseases. “We are mulling whether we can use their services as well. Then the work would become easier. But since dengue prevention work has also begun, we have to see how much their services can be used,” the official said.

There are also 1,400 civic personnel engaged in work related to information, education and communication on various diseases. But training them immediately to collect health data during door-to-door surveillance may not be easy, civic sources said.

Civic doctors were asked to intensify the surveillance at a meeting with state officials and local representatives of WHO on Tuesday.

“Community surveillance will help in early detection and isolation and thus prevent the spread,” said a public health specialist.