Acute Chagas disease (ACD) is caused by Trypanosoma cruzi. ACD outbreaks due to probable oral transmission occur regularly in small family gatherings that are exposed to contaminated foods. We studied two cohorts of residents on islands in the Breves and Bagre municipalities, in July and August 2007, to identify risk factors of transmission and to recommend preventative measures. Of the 25 cases identified in both cohorts, 13 (52%) were men, and the most frequent symptoms were fever (96%),asthenia (80%), myalgia (76%), abdominal pain (64%), retro-orbital pain, headaches and asthma (52%). We recommend detailed investigation of future outbreaks and other studies to better understand and control oral transmission of T. cruzi.