A Davenport restaurant has closed voluntarily while health officials investigate an e-coli outbreak. Eight cases of e-coli have been linked to the Azteca restaurant in north Davenport. A dozen people in the Quad Cities have been confirmed to be ill with e-coli poisoning, which causes diarrhea, upset stomach and chills. Scott County Medical Director Dr. Louis Katz warns against using antibiotics to treat the symptoms of e-coli poisoning.Karen Shephard, an environmental health specialist with the Scott County Medical Department, says investigators spent three hours at the Azteca restaurant and discovered some possible problems.Shephard and other officials will conduct training sessions for workers at the Mexican restaurant.