The incidence of malaraia in Chennai has come down. The number of cases detected till September this year is 25,977, compared to 29,941 last year. This a "substantial" decrease of 13.23 per cent, according to a Chennai Corporation health department assessment, is because of "intensive campaigning" on the aspects of primary health and preventive measures. The standing committee on health which met on Wednesday, reviewed the progress of work taken up as part of malaria control and prevention.