Cholera, an acute watery diarrheal disease caused by Vibrio cholerae 01 and, less commonly, by V. cholerae 0139, is a major global public health problem in developing countries, causing an estimated 100,000 deaths per year and resulting in major microeconomic and macroeconomic losses. Cholera in developing countries is often described as occurring in two epidemiological forms: epidemic and endemic (1). Although these terms represent extremes at ends of a continuum, the terms are conceptually useful.