Decision algorithm for Legionnaire’s disease case-finding and classification. * The decision courses based on interview data (left) and medical records (right) are not necessarily mutually exclusive. Information for some subjects was gathered in both tracts. † Data from patient interview. ‡ Data from medical records review § Suspect cases: a resident identified by case-finding who has entered the decision algorithm because his/her illness is to be evaluated as a case of Legionnaire’s disease; resident’s illness remains a suspect case until further categorized. ¶ Physicians reviewed available medical records for signs, symptoms, and diagnostic testing (e.g., chest x-ray) to determine if subject possibly had pneumonia consistent with Legionnaire’s disease. # Possible case: a subject whose illness has met all the criteria of a suspect case is labeled a possible case while outstanding information or testing is collected.