At least 30 people have been killed in the latest cholera outbreak in Nigeria's oil-rich Delta state's Isoko South community, a health official said on Monday.Steven Ofili, chief epidemiologist at the Delta state health ministry, said prompt response and physical attention of health workers had curbed the spread of the disease, Xinhua reported.According to the official, people of the local community had been facing challenges of cholera disease since 2010, when their main source of drinking water was polluted.He said, rather than seeking medical help at the local health centre, the people resorted to traditional medicines and self-medication to cure themselves."It was not until after the disease had claimed five lives that they (the local residents) brought it to the knowledge of the local authorities," the official said.Confirmed cases of cholera were promptly treated at the local health facility.In 2010, more than 30 people had died when the first cholera outbreak was recorded following the pollution of the main source of water supply in the same area of Delta state.Cholera, an infectious disease, causes severe watery diarrhoea, can lead to dehydration and even death if untreated.