Weapons of Mass Destruction (WMD)


Common Name(s) Shigellosis
Scientific Name(s) Shigella
Physical Attributes Gram-negative, facultatively anaerobic, nonsporulating, nonmotile rods
Geography World wide
Mode(s) of Transmission Person-to-person, contaminated foods (esp. by flies); drinking or swimming in contaminated water
Likely BW Form(s) Aerosol; contaminated water
Pathology Diarrhea, fever, and stomach cramps; later develop pains in their joints, irritation of the eyes, and painful urination (Reiter's syndrome)
Host(s) Humans
Vector/Dormant Form Food and water, somtimes transmitted by flies
Incubation Period 1-4 days
Fatality Low but S. dysenteriae strain has fatality of 5-15%
Vaccine None
Treatment Antibiotics: ampicillin, trimethoprim/sulfamethoxazole (also known as Bactrim or Septra), nalidixic acid, or ciprofloxacin

Shigellosis is an infectious disease caused by a group of bacteria called Shigella that affects the intestinal tract. The Shigella species are aerobic, nonmotile, glucose-fermenting, Gram-negative bacteria that are highly contagious. The Shigella germ is actually a family of bacteria that can cause diarrhea in humans. The bacteria are responsible for 5-10% of all diarrheal illnesses worldwide, and shigellosis is especially prevelent in developing areas with large population concentrations and inadequate sanitation systems.

Shigella are present in the diarrheal stools of infected persons while they are sick and for a week or two afterwards. Most Shigella infections are the result of the bacterium passing from stools or soiled fingers of one person to the mouth of another person. This happens when basic hygiene and handwashing habits are inadequate. Shigella bacteria can also be transmitted through contaminated food, drinking water, or swimming in contaminated water. Flies that breed in feces can transfer the bacteria and contaminate food or water.

The incubation period for shigellosis is 1-4 days. The symptoms of shigellosis include diarrhea, fever (up to 106 degrees Fahrenheit), and stomach cramps. The diarrhea is often bloody. Persons may develop pains in their joints, irritation of the eyes, and painful urination (Reiter's syndrome, a late complication of shigellosis). Hemolytic-uremic syndrome can occur after S. dysenteriae type 1 infection. Shigellosis usually resolves in 5 to 7 days. In some persons, especially young children and the elderly, the diarrhea can be so severe that the patient needs to be hospitalized. A severe infection with high fever may also be associated with seizures in children less than 2 years old. Some persons who are infected may have no symptoms at all, but may still pass the Shigella bacteria to others.

There is no vaccine to prevent shigellosis. However, the spread of Shigella from an infected person to other persons can be stopped by frequent and careful handwashing with soap.

Humans with mild cases of shigellosis recover without antibiotic treatment. For more sever cases, the antibiotics commonly used for treatment of shigellosis are ampicillin, trimethoprim/sulfamethoxazole (also known as Bactrim or Septra), nalidixic acid, or ciprofloxacin. Appropriate treatment kills the Shigella bacteria that might be present in the patient's stools, and shortens the illness. Some Shigella bacteria have become resistant to antibiotics and using antibiotics to treat shigellosis can make the bacteria more resistant in the future. During outbreaks, antibiotics are typically prescribed only for the most severe cases.

Antidiarrheal agents such as loperamide (Imodium) or diphenoxylate with atropine (Lomotil) are likely to make the illness worse and should be avoided as treatment for shigellosis.

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