IntroductionAs Thailand makes the transition from a developing country to an industrialized one, the shift from rural to urban living, increased life expectancy and other demographic changes are transforming the health problems of its population. For ex-ample, the incidence of bacillary dysentery detected by the government’s routine national surveillance system decreased more than 6-fold between 1991 and 1999, from 1.3/10 000 population per year to 0.2/10 000 population per year (1, 2). Over the past decade, the reported average annual incidence