Southeast Iowa health officials have confirmed a third case of a virulent type of E. coli in the region.  The latest case involving the bacteria was confirmed Monday by the Des Moines County Health Department. In Lee County last week, health officials confirmed two cases (one being a death).  The Iowa Department of Public Health says it has not determined the source of the illnesses.  Across the border in Hancock County, Ill., another possible case of E. coli was reported last Wednesday, but remained unconfirmed by state health officials.