Patterns of Shigella infection in families in rural Bangladesh.

To assess the mode of transmission of Shigella infection in rural Bangladesh, questionnaire and culture surveys were conducted in baris (neighborhoods) where persons with diarrhea associated with Shigella infection and index controls with non-Shigella diarrhea lived. Nineteen percent of persons in Shigella baris and 7% of persons in control baris were infected during the survey periods (P less than 0.001). The prevalence of Shigella infection was highest for children 1-9 years of age and for females than 39 years and was not related to socioeconomic status, family size or household crowding. Use of surface water for drinking was not a risk factor for Shigella infection; in fact, use of river water was more frequent in control baris. Both household and bari contacts of Shigella index cases frequently excreted different serotypes from that excreted by the person with the index case. In Shigella baris, families with infection were significantly more likely than uninfected families to have a history of an overnight stay away from home by a family member during the previous week. These observations suggest there were multiple introductions of Shigella into some families and that the epidemiology of Shigella infection for families in rural Bangladesh differs from that observed for families living in more industrialized countries.