Bengal on Friday reported 427 new Covid-19 cases, the highest 24-hour rise, taking the total number of patients past 7,000 and active cases beyond 4,000.

Chief minister Mamata Banerjee attributed the spike to the return of lakhs of migrant workers and others stranded elsewhere in the country. She said her government had accepted the challenge of planning and giving “loving shelter” to every returning migrant worker.

“The central government, without any planning, sent lakhs and lakhs of people. Without treatment, without food, not a paisa in hand. So, when they are coming now from Mumbai, Chennai, Gujarat, Indore, Delhi, many are arriving ill. So many have died on trains,” said Mamata.

Of the 427 new cases (till 9am on Friday), 408 — over 95 per cent — were from districts experiencing a high volume of returnees. The total cases rose to 7,303, which was 4,813 a week ago and 1,456 a month ago.

Calcutta has reported 101 new cases. The number of new patients in North 24-Parganas, Howrah, Hooghly and Malda are 65, 62, 44 and 34, respectively.

A positive element of the state’s Covid-19 stats for the day was the persistent rise in tests. With 9,686 tests reported on Friday, yet another record for 24 hours, Bengal’s tests per million count increased to 2,795. The total number of tests went past the 2.5 lakh mark to 2,51,517. A month ago, Bengal was recording around 2,500 tests a day, with 334 tests per million and a total test count of 30,141.

However, the positive confirmation rate — the percentage of people found infected among those tested — deteriorated from 2.6 a week ago to 2.9 per cent.

An increasing positive confirmation rate is indicative of higher levels of Covid-19 spread.

The state also reported 11 deaths from the novel coronavirus on Friday, taking the toll directly from the pathogen to 294. The state had earlier said 72 Covid-19 patients had died from comorbidities till April 30. Calcutta alone accounted for 238 of the 366 total deaths.

Bengal now has 11,504 quarantine facilities for returnees on Shramik Special trains and they together shelter 1,39,624 people.

This is over and above 1,51,848 people under home quarantine and 23,077 at 582 other state quarantine facilities.

The state had less than 5,000 people in institutional quarantine and less than 10,000 persons in home quarantine till May 8, after which the returns started.

“While 3.11 lakh people suddenly in quarantine is a worrisome number for any state, a big positive factor is that 2.18 lakh people have already completed quarantine successfully,” said a minister.

The total number of recovered cases rose to 2,912 with the release of 144 infected persons following cure. The total number of cured cases has seen a rise of 11 times in a month.

The recovery rate, which improved vastly from 18.2 per cent a month ago, was 39.87 per cent on Thursday. It had risen to 40.25 on Friday. Calcutta reported the most recoveries at 1,038.