Chennai, June 22 : The presence of Omicron's BA-5 sub-variant may be the reason for the sudden spike in cases in Tamil Nadu, the state Public Health and Preventive Medicine Department, said in its data for May-June. While only 4 per cent of cases caused by the sub-variant were identified in May, in June to date, the BA-5 sub-variant was identified in 25.2 per cent of the SARS- CoV-2 samples whose whole genome sequencing was conducted. BA-2.38 is the predominant Omicron sub-variant in Tamil Nadu and earlier, the BA-5 sub-variant had now gained currency among the samples leading to the sudden increase in number of Covid cases in the state. State Health Secretary P. Senthilkumar, in a statement on Wednesday, said that there was an increase in the BA-5 sub-variant, and the basic weapons to counter it remains masks, hand hygiene, physical distancing, and vaccination. Talking to IANS, state Health Minister Ma Subramanian said: "People must adhere to Covid -19 protocol as envisaged by the state Health Department and the presence of BA-5 sub-variant of the SARS- CoV 2 virus can be tackled by properly adhering to the Covid protocol. Moreover, everyone should take the vaccine to prevent the spread." /IANS