The dengue epidemic is raging mainly due to the current south-west monsoon, health officials have warned.Potential mosquito breeding grounds were mainly detected in schools and constructions sitesThe National Dengue Control Unit (NDCU) says most cases have been reported from Colombo, Gampaha, Kalutara, Galle, Ratnapura and Kandy districts.According to NDCU figures as of September 20, there were 45,000 cases this year with 70 deaths.