Abstract
Diarrheal diseases exact a considerable toll of morbidity and mortality worldwide, including in developed countries where the incidence of foodborne illness, in particular, may be increasing. This article summarizes the current understanding of the basis of diarrheal illness, focusing particularly on intracellular signaling mechanisms that limit the extent of intestinal epithelial chloride secretion, which may offer new targets for antidiarrheal therapies. Recent information regarding the mechanisms whereby invasive bacteria cause diarrhea is also reviewed along with effects of beneficial bacteria (so-called probiotics) in limiting dysfunction associated with enteric infections. Finally, the author provides some speculations as to the possible benefits to the host of mounting a diarrheal response to an offending pathogen, and possible consequences of the failure of this primitive host defense mechanism.