Epidemiology of leptospirosis in California: a cause of aseptic meningitis.

Twenty-one cases of leptospirosis, including three that were fatal, were reported in California during 1961-1965. An additional 18 cases were detected for the same period by screening sera from patients with central nervous system (CNS) disease of suspected viral origin. This finding supports a hypothesis that leptospirosis frequently is not considered in the differential diagnosis of CNS disease in which viral infection is suspected. The 39 patients, six of them females, ranged in age from six to 66 years. Most infections occurred in the summer. A history of exposure to animals or of swimming in potentially contaminated waters was obtained from 32 of the 39.