Chennai has recorded 1,775 confirmed dengue cases this month, along with more than 8,300 fever cases, Greater Chennai Corporation Commissioner G S Sameeran said on Tuesday. Nearly 70 per cent of dengue patients have recovered. The corporation has stepped up mosquito control, including drone-based larvicide spraying along the Cooum river near the Madras Medical College hostel. Drones will be used in waterways wider than 30 metres across all 15 zones, and will be extended to the Adyar river and Buckingham Canal. The corporation has deployed 3,703 field workers across 2,076 sectors to find and remove breeding sites. It has mapped 25,035 vacant plots and identified 539 mosquito hotspots. Tamil Nadu has recorded 17,651 dengue cases this year, up nearly 20 per cent from last year. Context: Dengue is a mosquito-borne viral illness that spreads fastest in stagnant water after rains. Health officials urged residents to keep surroundings dry and report fever cases early.