Sensex closed over 1,200 points lower on Monday as the index fell below the 78,000 level after India reported its first HMPV cases. Meanwhile, Nifty also closed nearly 400 points lower, dipping close to the 23,600 level. The top Sensex losers included Tata Steel, NTPC and Kotak Mahindra Bank while top Nifty losers included Trent, Bharat Petroleum and Coal India.