Here, we demonstrate that mice continuously colonized with E. coli producing ST in the colorectum exhibit normal growth, without evidence of diarrheal disease, representing a model that recapitulates otherwise healthy patients in endemic areas chronically colonized with ETEC. Indeed, while these mice remain asymptomatic, ST is secreted into their intestinal lumens, binding to GUCY2C and stimulating cGMP production and signaling. The gene discussed is GUCY2C; the disease is diarrheal disease.