Shigellosis is an infection of the colon (large intestine) caused by Shigella bacteria. Shigellosis is also called bacillary dysentery because it can cause severe diarrhea. However, the infection often causes only mild symptoms. Shigella can be found in water polluted with infected sewage. Bacteria commonly enter the body through a contaminated drinking supply. Shigella bacteria also can be found on food that has been rinsed with unclean water, grown in fields contaminated with sewage, or touched by flies that have touched feces. Shigella bacteria can reach the mouth on dirty fingers that have touched items soiled with feces, including dirty diapers, toilets and bathroom fixtures. Outbreaks of shigellosis are most common in areas where sanitation is poor, and in places where people live under confined or crowded conditions. Shigella also can be passed from person to person during anal-oral sex. Shigellosis is more common among children ages 1 to 4. Children of this age have a higher rate of infection because they are starting to use the toilet and often forget to wash their hands. Infants are at the highest risk of becoming seriously ill from a Shigella infection.  
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