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Shigella and Drinking Water from Private Wells
Shigellosis (shi-ghel-O-sis) is an infectious disease caused by a group of bacteria known as Shigella. Shigellosis is one of the most contagious types of diarrhea caused by bacteria. It is a common cause of waterborne outbreaks in the United States, though most of these outbreaks occur in recreational water rather than in drinking water.
For more information about shigellosis and treatment, please visit CDC's shigellosis page.
Shigella is found in every part of the United States and throughout the world. The bacteria can enter the water through various ways, including sewage overflows, sewage systems that are not working properly, and polluted storm water runoff. Wells may be more vulnerable to such contamination after flooding, particularly if the wells are shallow, have been dug or bored, or have been submerged by floodwater for long periods of time.
If you suspect a problem and your drinking water comes from a private well, you may contact your state certification officer for a list of laboratories in your area that will perform tests on drinking water for a fee.
To kill or inactivate Shigella, bring your water to a rolling boil for one minute (at elevations above 6,500 feet, boil for three minutes) Water should then be allowed to cool, stored in a clean sanitized container with a tight cover, and refrigerated.
Other short-term options for purifying drinking water that has been contaminated with Shigella include using an ultraviolet light-based device designed to inactivate bacteria in drinking water. Water may also be treated with iodine tablets, such as those intended for use while camping. However, iodine-based treatments do not protect against certain germs like Cryptosporidium, and they should be used only on a temporary or emergency basis.
Disinfecting your well may be a longer-term solution. Contact your local health department for recommended procedures. Have your well water tested regularly, at least once a year, after treatment to make sure that the problem does not recur.