Most of these areas are occupied by slumdwellers and there is no regular supply of water and residents end up storing water for several days encouraging mosquito breeding.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/panchkula-reports-lowest-malaria-cases-four-years
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/indian-express-chandigarh
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/haryana
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/panchkula-d
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/malaria
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/vector-borne-diseases
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/health-effects
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/health