General Information

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 ¹. 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 ².

Symptoms of shigellosis typically start 1–2 days after exposure and include:

• Diarrhea (sometimes bloody)
• Fever
• Abdominal pain
• Tenesmus (a painful sensation of needing to pass stools even when bowels are empty)

Symptoms of shigellosis generally begin 1 to 2 days after becoming infected with the bacteria.

In persons with healthy immune systems, symptoms usually last about 5 to 7 days. Persons with diarrhea usually recover completely, although it may be several months before their bowel habits are entirely normal. Once someone has had shigellosis, they are not likely to get infected with that specific type again for at least several years. However, they can still get infected with other types of Shigella.

Possible complications from Shigella infections include:

• Post-infectious arthritis. About 2% of persons who are infected with Shigella flexneri later develop pains in their joints, irritation of the eyes, and painful urination. This is called post-infectious arthritis. It can last for months or years, and can lead to chronic arthritis. Post-infectious arthritis is caused by a reaction to Shigella infection that happens only in people who are genetically predisposed to it ².
• Blood stream infections. Although rare, blood stream infections are caused either by Shigella organisms or by other germs in the gut that get into the bloodstream when the lining of the intestines is damaged during shigellosis. Blood stream infections are most common among patients with weakened immune systems, such as those with HIV, cancer, or severe malnutrition ².
• Seizures. Generalized seizures have been reported occasionally among young children with shigellosis, and usually resolve without treatment. Children who experience seizures while infected with Shigella typically have a high fever or abnormal blood electrolytes (salts), but it is not well understood why the seizures occur ².
• Hemolytic-uremic syndrome or HUS. HUS occurs when bacteria enter the digestive system and produce a toxin that destroys red blood cells. Patients with HUS often have bloody diarrhea. HUS is only associated with Shiga-toxin producing Shigella, which is found most commonly in Shigella dysenteriae ².

Many different kinds of germs can cause diarrhea, so establishing the cause will help guide treatment. Healthcare providers can order laboratory tests to identify Shigella in the stools of an infected person. The laboratory can also do special tests to determine which antibiotics, if any, would be best to treat the infection.

Diarrhea caused by Shigella usually resolves without antibiotic treatment in 5 to 7 days. People with mild shigellosis may need only fluids and rest. Bismuth subsalicylate (e.g., Pepto-Bismol®) may be helpful ^{3, 4}, but medications that cause the gut to slow down, such as loperamide (e.g., Imodium®) or diphenoxylate with atropine (e.g., Lomotil®), should be avoided ⁵. Antibiotics are useful for severe cases of shigellosis because they can reduce the duration of symptoms ⁶. However, Shigella is often resistant to antibiotics. If you require antibiotic treatment for shigellosis, your healthcare provider can culture your stool and determine which antibiotics are likely to work. Tell your healthcare provider if you do not get better within a couple of days after starting antibiotics. He or she can do additional tests to learn whether your strain of Shigella is resistant to the antibiotic you are taking.

In 2013, CDC declared antibiotic-resistant Shigella an urgent threat in the United States ⁷. Resistance to traditional first-line antibiotics like ampicillin and trimethoprim-sulfamethoxazole is common among Shigella globally, and resistance to some other important antibiotics is increasing ^8-13. While travelers to the developing world are at particular risk of acquiring antibiotic-resistant shigellosis, outbreaks of shigellosis resistant to ciprofloxacin or azithromycin—the two antibiotics most commonly used to treat shigellosis—have been reported recently within the United States and other industrialized countries ^14-18. About 27,000 Shigella infections in the United States every year are resistant to one or both of these antibiotics ⁷. When pathogens are resistant to common antibiotic medications, patients may need to be treated with medications that may be less effective, but more toxic and expensive. To learn more about antibiotic resistance, see Antibiotic / Antimicrobial Resistance.

Shigella infections are diagnosed through laboratory testing of stool specimens (feces). Healthcare providers can order tests to check which antibiotics are likely to help treat a particular patient’s infection. If you were treated with antibiotics for shigellosis but do not feel better within a couple of days, tell your healthcare provider. You may need additional tests to check whether your Shigella strain is resistant to the antibiotics.

Please follow the advice of your healthcare provider. If you do not feel better within a couple of days after beginning treatments, tell your healthcare provider. Protect others by washing your hands carefully with soap after using the toilet, and wait until your diarrhea has stopped before preparing food for others, swimming, or having sex.

Reducing the spread of antibiotic-resistant Shigella requires a multi-pronged approach: preventing infections, tracking resistance, improving antibiotic use, and developing new treatments ⁷. For more information, see Antibiotic Resistance Threats in the United States, 2013. [PDF – 114 pages].

Shigella germs are present in the stools of infected persons while they have diarrhea and for up to a week or two after the diarrhea has gone away. Shigella is very contagious; exposure to even a tiny amount of contaminated fecal matter—too small to see– can cause infection. Transmission of Shigella occurs when people put something in their mouths or swallow something that has come into contact with stool of a person infected with Shigella. This can happen when:

• Contaminated hands touch your food or mouth. Hands can become contaminated through a variety of activities, such as touching surfaces (e.g., toys, bathroom fixtures, changing tables, diaper pails) that have been contaminated by stool from an infected person. Hands can also become contaminated with Shigella while changing the diaper of an infected child or caring for an infected person.
• Eating food contaminated with Shigella. Food may become contaminated if food handlers have shigellosis. Produce can become contaminated if growing fields contain human sewage. Flies can breed in infected feces and then contaminate food when they land on it.
• Swallowing recreational (for example lake or river water while swimming) or drinking water that was contaminated by infected fecal matter.
• Exposure to feces through sexual contact.

• Wash your hands with soap carefully and frequently, especially after using the toilet.
• Do not prepare food for others while you are sick. After you get better, wash your hands carefully with soap before preparing food for others.
• For those who work in healthcare, food service, or childcare facilities should not prepare or handle food for others until their local health department has authorized them to return to work. Improvements in worker sick leave policies and providing adequate hygiene facilities and education for food service workers may prevent shigellosis caused by contaminated foods.
• Avoid swimming until you have fully recovered.
• Don’t have sex until several days after you no longer have diarrhea.

• Supervise handwashing of toddlers and small children after they use the toilet. Wash infants’ hands with soap and water after diaper changes.
• Dispose of soiled diapers properly, and clean diaper changing areas after using them.
  • Safe & Healthy Diapering in the Home
• Keep the child out of childcare and group play settings while ill with diarrhea, and follow the guidance of your local health department about returning your child to his or her childcare facility.
• Avoid taking your child swimming or to group water play venues until after he or she has fully recovered.

School and work exclusion policies differ by local jurisdiction. Check with your local or state health department to learn more about the laws where you live. It is critical to practice good hand-washing after changing diapers, after using the toilet, and before preparing or eating food to prevent the spread of these and many other infections.

• Providing municipal water service, this may be lacking in many lower income countries. Making municipal water supplies available and safe and treating sewage are highly effective prevention measures that have been in place for many years.
• Following these guidelines to make your food safer to eat. People with shigellosis should not prepare food or drinks for others until they are well. Food service workers should not prepare or handle food for others until their local health department has authorized them to return to work. Improvements in worker sick leave policies and providing adequate hygiene facilities and education for food service workers may prevent shigellosis caused by contaminated foods.
• At swimming beaches, providing enough bathrooms and handwashing stations with soap near the swimming area helps keep the water from becoming contaminated. For more information, see Swimming Hygiene.

• Exclude any child with diarrhea from the childcare setting until the diarrhea has stopped.
  • Children who have recently recovered from shigellosis can be grouped together in one classroom (cohorted) to minimize exposing uninfected children and staff to Shigella.
• Assign separate staff to change diapers and prepare or serve food.
• Reassign adults with diarrhea to jobs that minimize opportunities for spreading infection (for example, administrative work instead of food preparation).
• Establish, implement, and enforce policies on water-play and swimming that:
  • Exclude children ill with diarrhea from water-play and swimming activities.
  • Exclude children diagnosed with Shigella from water-play and swimming activities for an additional week after their diarrhea has resolved.
  • Have children and staff wash their hands before using water tables.
  • Have children and staff shower with soap before swimming in the water.
    • If a child is too young to shower independently, have staff wash the child, particularly the rear end, with soap and water.
  • Take frequent bathroom breaks or check their diapers often.
    • Change children’s diapers in a diaper-changing area or bathroom and not by the water.
  • Discourage children from getting the water in their mouths and swallowing it.
  • Prohibit the use of temporary inflatable or rigid fill-and-drain swimming pools and slides because they can spread germs in childcare facilities.

• Young children are the most likely to get shigellosis, but people from all age groups are affected ¹⁹. Many outbreaks are related to childcare settings and schools, and illness commonly spreads from young children to their family members and others in their communities because it is so contagious.
• Gay, bisexual, and other men who have sex with men (MSM)^† are more likely to acquire shigellosis than the general adult population ²⁰. Shigella passes from stools [poop] or soiled fingers of one person to the mouth of another person, which can happen during sexual activity. Many shigellosis outbreaks among MSM have been reported in the United States, Canada, Tokyo, and Europe since 1999 ^{8, 15, 16, 18, 21, 22}. For more information, see Shigella Infections among Gay & Bisexual Men.
• HIV-infected persons can have more severe and prolonged shigellosis, including having the infection spread into the blood, which can be life-threatening ²³.
• Large outbreaks of Shigella have occurred in traditionally observant Jewish communities ^24-26. Documented outbreaks in traditionally observant Jewish communities often begin in childcare settings and spread within and between households during social gatherings.
• Travelers to developing countries may be more likely to get shigellosis, and to become infected with strains of Shigella that are resistant to important antibiotics ^{27, 28}. Travelers may be exposed through contaminated food, water (both drinking and recreational water), or surfaces. Travelers can protect themselves by strictly following food and water precautions, and washing hands with soap frequently. For more information, see Travelers' Health – Food and Water Safety. 

^† The term men who have sex with men is used in CDC surveillance systems because it indicates the behaviors that transmit Shigella infection, rather than how individuals self-identify in terms of their sexuality.

Every year, there are about 500,000 cases of shigellosis in the United States ¹. Shigellosis does not have a marked seasonality, likely reflecting the importance of person-to-person transmission. For more information, see the FoodNet 2011 Surveillance Report.[PDF – 53 pages] 

In 2013, the average annual incidence of shigellosis in the United States was 4.82 cases per 100,000 individuals ²⁹.

Shigella infections have not declined appreciably over the past 10 years. The incidence rate of infection with Shigella sonnei decreased from 2008 through 2011, but increased in 2012 ^{30, 31}.

Resistance to traditional first-line drugs such as ampicillin and trimethoprim-sulfamethoxazole is common. Healthcare providers now rely on alternative drugs like ciprofloxacin and azithromycin to treat infections. However, strains of Shigella resistant to these antibiotics are becoming more common in the United States. Infections caused by antibiotic-resistant Shigella strains can last longer than infections caused by antibiotic-susceptible bacteria (bacteria that can be treated effectively with antibiotics) ⁷. Because initial treatment can fail, costs are expected to be higher for resistant infections ⁷. For more information, see Antibiotic / Antimicrobial Resistance.

• If you or your child have diarrhea, find more information to protect yourself, your family, and your community, as well as steps to get better.
• Handwashing is the #1 way to protect yourself against Shigella infections. Please see the CDC handwashing website for more information.

• Follow diapering procedures that will minimize exposure to germs that cause diarrhea. Please see Diaper-Changing Steps for Childcare Settings for more information.
• National Resource Center. Environmental Health in Early Care and Education Manual [PDF – 55 pages]
• American Academy of Pediatrics (AAP):
  • For health professionals
  • For early education and childcare providers
• Early Childhood Education Linkage System
  • Manuals/Pamphlets/Policies
  • Fact Sheets

• CDC Fact Sheet: Shigella Infections among Gay & Bisexual Men
• Minnesota Department of Health. Shigellosis Fact Sheet for MSM [PDF – 2 pages]
• Public Health England. Good Session? Bad Case of Diarrhoea? Maybe It's Shigella [PDF – 2 pages]

• CDC. Swimming Hygiene
• CDC. Recreational Water Illnesses (RWIs)
• CDC. Steps of Healthy Swimming
• CDC. Infographic: Clean It Up, Swimmers

• New York City Department of Health.
  • Wash Your Hands, Observant Adults. [PDF – 1 page]
  • Wash Your Hands, Observant Kids. [PDF – 1 page]

Below you will find useful links related to hygiene and handwashing in the food service industry.

• CDC. Food Worker Handwashing and Restaurant Factors
• CDC. Using Employee Health and Personal Hygiene Measures
• CDC. Studies on Restaurant Food Handling and Food Safety Practices