Seizures can occur, triggered by a toxin released by the germ. In fact, sometimes the seizure is the first manifestation of illness in a previously healthy child with no seizure history in the past. The mystery is solved when the child subsequently has a large diarrhea stool, which subsequently tests positive for Shigella bacteria. Animals do not harbor this germ. Eating or drinking contaminated food or water or contact with a contaminated toy or other object also are important modes of transmission of the disease.
Patients are thus contagious until the germ is no longer present in the feces.
Even without antibiotic treatment, the carrier state usually ceases within 4 weeks of the beginning of illness. A chronic carrier state is rare, which differentiates Shigella from Salmonella infections. Again in contrast to the management of Salmonella infections, symptomatic patients with Shigella infections are treated with antibiotics.