Many infectious and parasitic diseases, especially those newly emerging or reemerging, present a difficult diagnostic challenge because of their obscurity and low incidence.Important clues that could lead to an initial diagnosis are often overlooked, misinterpreted, not linked to a disease, or disregarded.We constructed a computer-based decision support system Side Rails containing 223 infectious and parasitic diseases and used it to conduct a historical intervention study based on field investigation records of 200 cases of Clothing - Junior Tops - Sleeveless human brucellosis and 96 cases of murine typhus that occurred in Texas from 1980 through 1989.Knowledge-based screening showed that the average number of days from the initial patient visit to the time of correct diagnosis was significantly reduced (brucellosis--from 17.
9 to 4.5 days, p = 0.0001, murine typhus--from 11.5 to 8.
6 days, p = 0.001).This study demonstrates the potential value of knowledge-based patient screening for rare infectious and parasitic diseases.