Shigella is a genus of gram-negative bacteria that are responsible for causing shigellosis, a severe form of diarrhea that can be life-threatening if left untreated. Shigellosis is a major public health concern, especially in developing countries with prevalent poor sanitation and hygiene practices.

The pathogenesis of Shigella is complex and involves several virulence factors, including the ability of the bacteria to invade and replicate within the intestinal epithelium. Shigella also produces several toxins, including Shiga toxin and lipopolysaccharide endotoxin, which can cause inflammation, tissue damage, and dysentery.

The symptoms of shigellosis typically begin with diarrhea, fever, and abdominal cramps. Diarrhea can be watery or bloody and may be accompanied by mucus or pus. In severe cases, shigellosis can lead to dehydration, electrolyte imbalances, and even death.

The transmission of Shigella occurs primarily through the fecal-oral route, typically by consuming contaminated food or water or coming into contact with contaminated surfaces or objects. The bacteria can also be spread through person-to-person contact, especially in crowded or unsanitary conditions.

In recent years, Shigella infections have continued to pose a significant public health challenge globally. The World Health Organisation (WHO) was notified on 4 February 2022 of an unusually high number of cases of extensively drug-resistant (XDR) Shigella sonnei which have been reported in the United Kingdom of Great Britain and Northern Ireland and several other countries in the WHO European Region since late 2021. Although most infections with S. sonnei result in a short duration of disease and low case fatality, multi-drug resistant (MDR) and XDR shigellosis is a public health concern since treatment options are very limited for moderate to severe cases.

Shigellosis is endemic in most low- or middle-income countries (LMICs) and is a major cause of bloody diarrhea worldwide. Each year, it is estimated to cause at least 80 million cases of bloody diarrhea and 700 000 deaths. Almost all (99%) Shigella infections occur in LMICs, and the majority of cases (~70%), and of deaths (~60%), occur among children less than five years of age. It is estimated that <1% of cases are treated in the hospital.

In addition, the emergence of antibiotic-resistant strains of Shigella has become a growing concern, with many regions reporting increasing rates of resistance to common antibiotics used to treat shigellosis. While efforts to improve sanitation and hygiene practices and promote the appropriate use of antibiotics is underway, continued vigilance and collaboration across the global health community are needed to address the ongoing threat of Shigella infections.

Treatment for shigellosis typically involves antibiotics, but resistance to commonly used antibiotics is becoming increasingly common. Therefore, prevention measures, such as improving sanitation and hygiene practices, ensuring safe food and water sources, and promoting the appropriate use of antibiotics, are critical for controlling the spread of Shigella and reducing the incidence of shigellosis.