Newsline found another possible cause: dirt. Kharak Raveda village has no sewage network, its streets are full of cowdung, sewage and puddles; illegal supply lines are drawn from tubewells
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/contaminated-water-responsible-chattarpur-gastro-outbreak-says-mcd
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/indian-express-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/tubewells
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-quality
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/rural-water-supply
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/health-effects
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/waterborne-diseases
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/health
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/municipal-corporations
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/delhi
[11] http://admin.indiaenvironmentportal.org.in/category/thesaurus/delhi-jal-board-djb