Persistent diarrhea (PD; duration >/=14 days) is a growing part of the global burden of diarrheal diseases. A 45-month prospective cohort study (with illness, nutritional, and microbiologic surveillance) was conducted in a shantytown in northeastern Brazil, to elucidate the epidemiology, nutritional impact, and causes of PD in early childhood (0-3 years of age). A nested case-control design was...