The administration should closely monitor Covid patients’ Ct (cycle threshold) value, considered a key indicator of the viral load in an infected person, to keep potential super-spreaders in check, Mamata Banerjee said on Tuesday.

Ct is a number indicating the presence of a gene in a swab sample. The lower the Ct value for a specific gene, the higher the presence of that gene in the sample. In Covid-19, a high Ct value is considered to indicate a lower viral load.

Bengal on Tuesday reported 3,370 new Covid-19 patients — the highest intra-day spike — 63 deaths and 3,036 recoveries.

The chief minister stressed the need to keep tight vigil on Covid-19 patients with Ct value of less than 20.

Mamata was speaking to officials at an administrative review meeting for West Midnapore in Kharagpur when she asked district magistrate Rashmi Kamal — a physician — and the chief medical officer of health if they had been monitoring those with low Ct values.

“Track the Ct values; the lesser the Ct value, the more dangerous that infected person is, by way of his/her ability to spread the disease. Ct value is being given as part of the results now,” the chief minister said after realising the administration hadn’t been doing it.

Mamata, also the health minister, instructed chief secretary Alapan Bandyopadhyay to make a note of it for conveying to all concerned.

Although there is no conclusive evidence to correlate Ct value with the contagiousness of the novel coronavirus, it is being considered an important indicator of viral load and most Bengal laboratories approved for Covid-19 tests have been reporting it in their results for more than two months now.

“Categorise them into A, B and C groups for tight vigil,” Mamata said while asking former chief secretary Rajiva Sinha to explain what it meant.

Sinha, currently the chairman of the West Bengal Industrial Development Corporation, said every Covid positive result from laboratories now came with the Ct value mentioned.

“If the Ct value is higher than 20, that person is likely to be less of a spreader of the infection. If the value is less than 20… the lower it is, the riskier it is. That indicates higher viral load and the ability to spread the disease more and infect more people,” Sinha said.

“The chief minister has been saying this repeatedly to us and the health department has been issuing instructions… monitoring those with Ct values less than 20 is important,” he said.

It must be done daily, the chief minister added. The districts administration must locate those with Ct value of less than 20 on its daily list of new cases. “These people will not only spread the disease more but also be more ill than other infected people. This is over and above the monitoring of co-morbidities…. This must be kept in view and monitored closely; a lot of problems will then be solved.”

“If such people do not wear masks, do not adhere to Covid-19 protocols, they can infect 20-22 others. Even in home isolation, such persons have to be kept under cautious watch,” she said. “Such simple concepts: Ct value, co-morbidities… if we are aware of these and ensure incisive intervention, this pandemic can be better managed.”

Sinha stressed the need for close monitoring of all active cases daily. “Only the active cases (per district) is not very tough to keep track. Especially the sixth and 10th days… you know are potentially very risky days. For those days, categorise them as red and track them so that there is timely hospitalisation for those in need.”

With the 3,370 new cases, the state’s total case count went past 277,000, of which close to 244,000 are recoveries, besides 5,318 deaths.

The recovery rate continued to rise and reached 87.98, still ahead of the national rate of 84.68 per cent.

Of the 63 deaths, 16 died in the city and 15 in North 24-Parganas.

As of Tuesday, the state government reported 4,515 or 84.9 per cent as deaths with comorbidity “present”.

Bengal’s overall mortality rate improved to 1.91; still behind the national rate of 1.54 per cent.

The state logged 42,382 tests on Tuesday, which took the total past 348,000 at 38,672 tests for every million people.

The positive confirmation rate remained at 7.96 per cent.

The state reported 38 per cent occupancy of the 12,715 Covid beds in 92 hospitals and more than 299,000 telemedicine consultations.