Shigellosis, commonly referred to as bacillary dysentery, is an infectious disease caused by the Shigella bacteria. Most individuals infected with Shigella develop symptoms such as diarrhea, fever, and stomach cramps, which typically manifest one to two days after exposure. The diarrhea is often bloody and can be quite severe, particularly in vulnerable populations like young children and the elderly, sometimes requiring hospitalization. Severe infections may also present with high fever, potentially leading to seizures in children under two years old. Notably, some infected individuals may remain asymptomatic but can still carry and transmit the Shigella bacteria to others.

There are several species of Shigella bacteria. Shigella sonnei, also known as “Group D,” is responsible for a significant proportion of infections in the United States and is frequently associated with foodborne transmission, although shigellosis accounts for less than 10% of reported foodborne illness outbreaks in the country. A second type, Shigella flexneri (or “Group B”), accounts for most of the remaining infections in the U.S., with studies indicating a significant percentage of these cases are sexually transmitted. Other strains, such as Shigella dysenteriae type 1, are typically found in water contaminated with human feces. While these strains are rare in the U.S., they remain significant causes of morbidity and mortality in developing countries.

Shigellosis is more prevalent in the summer months compared to winter. Children, particularly toddlers aged 2 to 4, are at the highest risk for shigellosis, with many cases occurring in child-care settings or through family transmission.

Recently, an increase in multidrug-resistant cases of shigellosis has been reported in the U.S., often linked to travelers returning from abroad. Strains such as Shigella sonnei have shown resistance to ciprofloxacin, a primary antibiotic used for treatment in adults, while Shigella is already resistant to ampicillin.

Shigella is often found in water contaminated with human feces. Common food sources include salads (such as potato, tuna, shrimp, macaroni, and chicken), raw vegetables, dairy products, and poultry. Contamination typically occurs through the fecal-oral route, primarily due to exposure to polluted water or unsanitary food handling practices by food handlers.

In the United States, an estimated 500,000 cases of shigellosis occur annually, contributing to approximately 600,000 deaths worldwide each year. While the exact number of infections attributed to contaminated food is unknown, given that only a small amount of Shigella can cause infection, this figure is likely considerable. Most related deaths happen in developing countries with inadequate sanitation and unsafe water supplies.

The diagnosis of shigellosis is primarily made through laboratory testing of stool samples. When a patient presents symptoms consistent with shigellosis, such as diarrhea (especially if bloody), fever, and abdominal cramps, healthcare providers may recommend a stool culture. This test involves culturing the stool sample in a laboratory setting to identify the presence of Shigella bacteria.

In some cases, more advanced techniques such as polymerase chain reaction (PCR) may be used to detect Shigella DNA in the sample, allowing for a more rapid and accurate diagnosis. Additional tests may be performed to determine the specific strain of Shigella, which can inform treatment and control strategies, especially in cases of antibiotic-resistant infections.

Rapid detection methods can be valuable for outbreak investigations, enabling public health officials to identify sources of contamination and implement timely interventions to prevent further transmission. With the rising prevalence of multidrug-resistant strains, accurate detection is critical for effective management of Shigella infections and their potential spread in communities. 

Early diagnosis and appropriate treatment are essential to minimize complications and reduce the risk of transmission to others.