Leptospirosis on Kauai: investigation of a common source waterborne outbreak.

During the summer of 1987, a common source waterborne outbreak of leptospirosis occurred on the island of Kauai in the state of Hawaii. Eight leptospirosis cases were identified using the microscopic agglutination test. Methodologic weaknesses in this technique were responsible for the initial missed diagnosis on six of the eight cases. All cases had repeated exposure to the Waimea River. A wide array of animal reservoirs and optimal water conditions may have been factors in this outbreak.