Overview

Shigella is a genus of bacteria responsible for shigellosis, an infection of the intestinal lining. It is highly contagious, spreading through contaminated food, water, or direct contact with an infected person. This bacterial infection is particularly common in environments with poor sanitation, including schools, daycare centers, and crowded housing conditions.

In the United States, an estimated 450,000 cases of shigellosis occur each year, primarily affecting children under age five and individuals with weakened immune systems. Although most cases resolve on their own within a week, complications can arise, especially in vulnerable populations. Prompt diagnosis and treatment help reduce the duration and prevent further transmission.

Common Symptoms

Symptoms of shigellosis usually appear within 1 to 3 days after exposure and can persist up to a week or more. In some cases, mild symptoms linger for up to a month.

Symptoms include watery or bloody diarrhea, mucus or pus in stool, sudden abdominal cramps, rectal pain or tenesmus, nausea, vomiting, and fever. Diarrhea caused by Shigella can lead to dehydration, which is especially dangerous for young children and older adults.

Signs of dehydration include intense thirst, dry mouth, decreased urination or dark-colored urine, fatigue, and dizziness. In children, you may notice a lack of tears when crying, no wet diapers for over 3 hours, high fever, or extreme sleepiness.

Causes and Transmission

Shigella infection occurs when the bacteria enter the digestive tract. The primary mode of infection is through the fecal-oral route, where bacteria are ingested through contaminated hands, food, or water. Even a very small amount of Shigella can cause illness, which makes it particularly easy to spread in close-contact settings.

Infected individuals can carry and transmit the bacteria even if they are asymptomatic or after their symptoms have subsided. This makes effective hygiene and public health control critical.

Transmission often occurs through consuming food prepared by someone infected, drinking untreated or contaminated water, swimming in untreated water sources, changing diapers, or engaging in sexual contact with someone carrying the bacteria.

The most common strains include:

  • Shigella sonnei: The dominant strain in the U.S.

  • Shigella flexneri: Also common domestically

  • Shigella dysenteriae: Causes more severe infections and is found more frequently in developing countries

At-Risk Populations

Shigellosis can affect anyone but is particularly dangerous for certain demographics. Children under five are especially susceptible due to underdeveloped immune systems and less consistent hygiene practices. Daycare and school environments often contribute to outbreaks due to shared facilities and close contact.

Other at-risk groups include:

  • Residents or travelers in areas with poor sanitation

  • Men who have sex with men

  • Individuals with HIV/AIDS or diabetes

  • Cancer patients undergoing chemotherapy

  • Elderly individuals

  • People in long-term care facilities or shelters

Diagnosis Methods

If you suspect shigellosis, a healthcare provider will assess your symptoms, ask about recent travel or potential exposures, and may perform a physical examination. A stool sample is typically collected and cultured to confirm the presence of Shigella bacteria.

Blood tests may be performed to evaluate white blood cell counts and electrolyte levels to detect dehydration and inflammation. These diagnostic tools not only confirm the infection but also guide treatment choices, especially when considering antibiotic resistance.

Treatment Options

While some cases of shigellosis resolve on their own, treatment can alleviate symptoms, shorten illness duration, and prevent the spread to others. Treatment strategies include antibiotics, hydration support, and symptom management.

Antibiotic therapy is often used in moderate to severe cases. Common antibiotics include ciprofloxacin, ceftriaxone, and azithromycin. However, resistance is increasing globally, so treatment should ideally follow stool culture and sensitivity testing. Misuse or overuse of antibiotics may lead to treatment failure and complications.

Self-care is essential to avoid dehydration. Oral rehydration solutions are especially effective because they replenish electrolytes lost through diarrhea. People should avoid over-the-counter anti-diarrheal medications like Imodium, which can prolong the infection. Diuretic medications may also need to be paused under medical supervision.

Severe dehydration may necessitate hospitalization. In such cases, intravenous fluids and close monitoring are administered, particularly for children and the immunocompromised.

Prevention Tips

Preventing shigellosis largely depends on good hygiene and food safety. These measures significantly reduce the risk of infection:

  • Handwashing: Wash hands with soap and water before meals, after using the bathroom, and after changing diapers or assisting someone who is ill.

  • Safe diapering practices: Dispose of used diapers in lined trash cans, disinfect changing surfaces, and wash both adult and child’s hands immediately afterward.

  • Water safety: Avoid swallowing water in pools, lakes, rivers, or ponds, especially if not chlorinated or filtered properly.

  • Food hygiene: Avoid raw or undercooked foods, particularly while traveling. Drink bottled or treated water in areas where sanitation is poor.

  • Sexual health: Avoid sexual contact with individuals who currently have or recently recovered from shigellosis, ideally waiting two weeks after symptoms have fully resolved.

Travelers should be especially cautious, adhering to safe food and water practices. Avoiding street food, peeling fruits, and using water purification tablets can help reduce risk.

Complications

Although many people recover without any long-term effects, some may experience complications depending on the severity of the infection and their overall health.

Reactive arthritis is a form of joint inflammation that may develop after the infection has cleared. It typically includes joint pain, urinary discomfort, and eye inflammation. This condition usually resolves in a few months but can become chronic in rare cases.

Bacteremia, or bloodstream infection, is a rare but serious outcome, particularly in people with weakened immune systems. This condition can lead to sepsis, a life-threatening systemic response that requires urgent medical attention.

Seizures can occasionally occur, especially in children. They are often linked to high fever, electrolyte imbalance, or neurological irritation. While alarming, these seizures generally resolve without lasting harm.

Hemolytic-uremic syndrome (HUS) is one of the most severe complications, primarily affecting children. It involves the destruction of red blood cells and can lead to acute kidney failure. HUS may result from antibiotic-resistant strains of Shigella and often requires hospitalization and intensive care.

Shigella can also trigger chronic digestive issues in some individuals, including prolonged bloating, cramping, or irritable bowel syndrome-like symptoms. These may require additional management after the infection has resolved.

Recovery and Outlook

With prompt care, most people recover from shigellosis within one week. Mild gastrointestinal discomfort may persist for several days after other symptoms subside. Staying hydrated, maintaining good nutrition, and getting adequate rest will support a full recovery.

High-risk individuals may need follow-up visits to monitor kidney function, joint pain, or persistent gastrointestinal symptoms. In cases of resistant Shigella strains, extended treatment with second-line antibiotics may be required.

To avoid reinfection, individuals should adhere strictly to hygiene recommendations. Reinfection is possible due to the short-lived and strain-specific nature of immunity to Shigella.

Educating family members and caregivers about prevention methods is especially important to reduce the spread in households, schools, and caregiving facilities.