Shigellosis

Contact Precautions

Shigellosis, also known as bacillary dysentery, is an acute intestinal infection characterized by severe diarrhea and caused by the bacterium Shigella, a short, nonmotile, gram-negative rod. Shigella can be classified into four groups, all of which may cause shigellosis: group A (S. dysenteriae), which is most common in Central America and causes particularly severe infection and septicemia; group B (S. flexneri); group C (S. boydii); and group D (S. sonnei). Typically, shigellosis causes a high fever (especially in children) along with acute, self-limiting diarrhea with tenesmus and, possibly, electrolyte imbalance and dehydration. Shigellosis is most common in children ages 1 to 4; however, many adults acquire the illness from children.

The prognosis is good. Mild infections usually subside within 10 days; severe infections may persist for 2 to 6 weeks. With prompt treatment, shigellosis is fatal in only 1% of cases, although mortality may reach 8% in a severe S. dysenteriae epidemic.

Causes

Transmission occurs through the fecal-oral route, by direct contact with contaminated objects, or through ingestion of contaminated food or water. Occasionally, the housefly is a vector.

Shigellosis is endemic in North America, Europe, and the tropics. In the United States, about 20,000 to 30,000 cases are reported annually, usually in children or in elderly, debilitated, or malnourished adults. Worldwide, 150 million cases are reported each year. Shigellosis commonly occurs among confined populations, such as in mental institutions and day-care centers.

Complications

Although not common, complications may be fatal in children and in those who are debilitated. Such complications include electrolyte imbalances (especially hypokalemia), metabolic acidosis, and shock. Less common complications include conjunctivitis, iritis, arthritis, rectal prolapse, secondary bacterial infection, acute blood loss from mucosal ulcers, and toxic neuritis.

Assessment Findings

The patient’s history commonly reveals crowded living conditions and family members or close contacts with acute diarrhea. After an incubation period of 12 hours to 2 weeks (3 days is the average), Shigella organisms invade the intestinal mucosa and cause inflammation. In children, shigellosis usually produces a high fever, diarrhea with tenesmus, nausea, vomiting, irritability, drowsiness, and abdominal pain and distention. Within a few days, the child’s stool may contain pus, mucus, and—from the superficial intestinal ulceration typical of this infection—blood. Without treatment, dehydration and weight loss are rapid and overwhelming.

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