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Shigella Infection

Shigellosis facts*

*Shigellosis facts by John P. Cunha, DO, FACOEP

  • Shigellosis is an infectious disease caused by a group of bacteria called Shigella. There are four species of Shigella:
    • Shigella sonnei (the most common species in the U.S.)
    • Shigella flexneri
    • Shigella boydii
    • Shigella dysenteriae
  • The transmission of most Shigella infections is caused by the bacterium passing from stools or soiled fingers of one person to the mouth of another person. This happens when basic hygiene and hand-washing habits are inadequate and can happen during certain types of sexual activity. It may also be acquired from eating contaminated food.
  • Shigella is highly contagious and being exposed to even a miniscule amount of contaminated fecal matter can cause infection.
  • Risk factors for getting Shigella infection include living or traveling in areas where sanitation is lacking such as developing countries, being a toddler or changing toddler diapers, living or spending time in large institutional facilities (nursing homes, community pools, military barracks, jails), and being a sexually active gay man.
  • Outbreaks of Shigella can occur in child-care facilities and schools or when food is not properly handled. An outbreak of Shigella was reported in Flint, Mich., in October 2016. The lead-contaminated water in the town is causing residents to avoid exposure to it, which has lead to reduced hand washing and the spread of the bacteria.
  • Signs and symptoms of Shigella infection include diarrhea (often bloody), fever, stomach cramps, abdominal pain, and feeling as if you need to have a bowel movement even when bowels are empty (tenesmus), starting a day or two after exposure to the bacteria. This is the incubation period.
  • Women infected with Shigella during pregnancy need to ensure they do not become dehydrated or experience electrolyte imbalances due to diarrhea from the illness.
  • The diagnosis of shigellosis is made using laboratory tests to identify Shigella in the stools of an infected person. Tests can also be performed to determine which antibiotics may be used to best treat the infection.
  • Treatment for mild Shigella infection usually involves just rest and fluids, and the illness resolves on its own without antibiotics.
  • Over-the-counter treatment may include bismuth subsalicylate (Pepto-Bismol). Antidiarrheal drugs such as loperamide (Imodium) or diphenoxylate with atropine (Lomotil) can make the illness worse and should be avoided.
  • Antibiotics can shorten the duration of the illness and kill the Shigella bacteria. Shigella can be resistant to some antibiotics, so a doctor will perform a stool test to see which antibiotics may help. Antibiotics commonly used to treat Shigella are ampicillin, trimethoprim/sulfamethoxazole (Bactrim, Septra), ceftriaxone (Rocephin), or ciprofloxacin.
  • Precautions can prevent the spread of Shigella. Prevention includes hand washing with soap, basic food-safety preparations, proper disposal of soiled diapers, and avoiding swallowing water from ponds, lakes, or untreated pools.
  • The prognosis for shigellosis is generally good and most people recover even without medications within five to seven days.

What is shigellosis?

Shigellosis is a diarrheal disease caused by a group of bacteria called Shigella. Shigella causes about 500,000 cases of diarrhea in the United States annually. There are four different species of Shigella:

  • Shigella sonnei (the most common species in the United States)
  • Shigella flexneri
  • Shigella boydii
  • Shigella dysenteriae

S. dysenteriae and S. boydii are rare in the United States, though they continue to be important causes of disease in the developing world. Shigella dysenteriae type 1 can cause deadly epidemics.

Medically Reviewed by a Doctor on 10/19/2016


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