In Phase 4, NEA further expanded the study sites beyond Tampines West and Nee Soon East to cover more areas in Tampines and Yishun. The Phase 4 release sites cover about seven times the number of HDB blocks as Phase 1. This expansion allowed NEA to continue to develop and test release tactics for use in future deployment efforts.
Phase 4 findings
Ongoing releases have kept urban Aedes aegypti populations at levels that pose low dengue risk for more than a year—an unprecedentedly long period of low mosquito population for these areas. This has allowed NEA to reduce the number of male Wolbachia-Aedes mosquitoes released while still maintaining suppression. Along with the 90% reduction in mosquito population, NEA’s preliminary analysis also showed that in 2019, there were 65-80% less dengue cases in the Tampines and Yishun release sites, compared to areas without release.