By Chris Woolston, M.S.
What is shigellosis?
There are some types of germs that you definitely don't want to find in your next meal or glass of water. Add Shigella bacteria to the list. These highly contagious germs cause shigellosis, an illness marked by severe bouts of diarrhea. Shigellosis is a major threat -- especially in the developing world. According to the World Health Organization, the disease strikes about 120 million people in poor countries worldwide each year. Another 1.5 million people in industrialized countries develop the illness annually. The Centers for Disease Control and Prevention receives reports of about 14,000 cases in the United States each year, mostly in children between the ages of 2 and 4. But because most incidents are never reported, the true number of U.S. cases may be as much as 20 times higher.
More than one million people worldwide die of shigellosis each year -- over half of them young children.
How do people catch shigellosis?
Person-to-person contact -- unknowingly putting something into your mouth that has been contaminated with feces from someone who already has shigellosis -- is the usual method of transmission. Once Shigella reaches a person's digestive system, it takes the quick way out. The feces of an infected person will be loaded with germs for up to a couple of weeks, creating all sorts of opportunities for new infections. Toddlers who haven't completely mastered bathroom hygiene often catch the illness or spread it to people around them. Food handlers who don't wash their hands after using the bathroom can easily pass the germ to others. And according to the CDC, shigellosis can be sexually transmitted by direct or indirect oral-anal contact. Shigella bacteria can also lurk in raw produce or water that has been contaminated with human feces. In the United States, public drinking water is almost always safe, but the germ can invade private wells, especially after a major flood. Whatever the source, just 10 cells can be enough to start a new case of shigellosis.
Where is shigellosis most common?
Most cases of shigellosis occur in poor, overcrowded countries that lack basic sanitation. War, natural disasters, and other disruptions can cause upsurges in the disease. In industrialized countries, the disease is especially common in daycare centers and other places where lots of young children mingle.
What are the symptoms of shigellosis?
Shigella doesn't always cause a serious illness, and some people don't notice any symptoms at all. The less fortunate may start suffering diarrhea one to three days after picking up the germ. The diarrhea can range from mild to severe and may be watery or bloody. Other possible symptoms include fever, nausea, vomiting, and stomach cramps. Children under 2 may develop high fevers that can cause seizures. The illness generally lasts four to seven days.
How is shigellosis diagnosed?
Since many different germs can cause diarrhea, doctors won't be able to diagnose shigellosis without running a test. The doctor will send a stool sample to a laboratory that can look for the germs. Accurate diagnosis is important to help doctors choose the right treatment. Cases of shigellosis should be reported to public health officials; usually the laboratory conducting the tests will take care of this.
What is the treatment for shigellosis?
Antibiotics that kill the Shigella bacteria -- such as ampicillin or (for adults) ciprofloxacin -- are the best treatment for shigellosis, and can help shorten the illness by a couple of days. However, people with mild cases will likely recover pretty quickly without any treatment. In severe cases, prompt treatment can save lives. Unfortunately, some strains of Shigella have developed resistance to common antibiotics, so when there are many cases in a community, doctors may treat only the severe cases with antibiotics. Patients might be tempted to try over-the-counter anti-diarrhea treatments such as Imodium, but these medications can actually make the illness worse. Drinking plenty of fluids to keep up with water loss may be all the treatment you need, and this is generally the best way to respond to diarrhea.
How can shigellosis be prevented?
Basic hygiene is the best protection against shigellosis (and lots of other bacterial illnesses.) Parents should be sure to wash hands after changing dirty diapers. Hard as it may be, it's also important to teach young children to wash their hands after using the bathroom. If a young child has been diagnosed with shigellosis, hygiene has to rise to a new level. Disposable diapers need to go immediately into a trash can with a closed lid, and the changing area has to be disinfected with Lysol or a similar product after every use. Cloth diapers must be washed in hot, soapy water and dried in a hot dryer. Adults and older children with shigellosis must take extra time to wash their hands with soap and water after using the bathroom. Stay home from school or work as long as the diarrhea lasts, and do not prepare food until you have been free from diarrhea for at least two days.
Wells that have been contaminated with Shigella can be treated with disinfectants. Your local health department can tell you how to do this. Periodic testing should be conducted to make sure the germ hasn't returned.
If you're traveling in an area with poor sanitation, it's always a good idea to be careful about what you eat and drink. The CDC recommends drinking bottled or boiled water and eating only fully cooked foods or fruits you can peel yourself.
Centers for Disease Control and Prevention. Shigellosis. November 2009.
World Health Organization. Diarrhoeal Diseases: Shigellosis. 2009.
Centers for Disease Control and Prevention. Shigella sonnei outbreak among men who have sex with men -- San Francisco, California, 2000 - 2001. MMWR, October 26, 2001.
Centers for Disease Control and Prevention. Shigella and drinking water from private wells. 2003.
US Food and Drug Administration. Shigella spp.
Mayo Clinic. Shigella infection. April 2010.
Kent County Health Department. Shigellosis Fact Sheet. 2004.
Wisconsin Division of Public Health, Department of Health & Family Services. Shigellosis. July 2010.
Last Updated: March 11, 2013
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