Chennai: The IIT-Madras Covid cluster continues to see a surge in positive cases, with 33 more returning positive, taking the tally to 145 on Wednesday.

Tamilnadu Health Secretary Dr.J.Radhakrishnan, talking to reporters here after reviewing the situation in the IIT-M campus, said the whole Genome Sequencing of 25 samples from the cluster identified BA.2, a sub-variant of Omicron, and no new variant was detected.

Of the 1,892 samples tested on Tuesday night, 33 returned positive, registering a positivity rate of 1.7 per cent. Since April 19, when the cluster was identified, the cumulative positivity rate was 2.9 per cent.

A total of 145 persons tested positive out of the 4,974 samples tested so far. Of the 1,023 samples tested yesterday, 32 returned positive.

‘All the initial 25 samples that were sent from the IIT Madras cluster for Whole Genome Sequencing were of the BA.2 sub-variant of Omicron and no new variant was detected. Already, in March, 93 per cent of the Whole Genome Sequencing results had revealed the BA.2 sub-variant in the State,’ he said.

According to data released by the Health Department, there were a total of 7,490 students in the 19 hostels. So far, 4,974 persons in 26 locations on the campus, including the 19 hostels, were tested.

A total of 2,729 persons in the 19 hostels should be tested. Of them, only 19 remained to be tested at Mandakini Hostel, which had a total of 1,077 students. Mandakini Hostel bore the brunt with the most number of Covid-19 cases, at 38.