Shigella has been making people sick for thousands of years. Reports of the violent diarrheal illness it causes appear in ancient records, and the bacterium itself was formally identified in 1897 during a devastating outbreak in Japan that killed 20,000 people in just six months. The scientist who isolated it, Dr. Kiyoshi Shiga, gave the infection his name. More than a century later, the world is still struggling to bring it under control.
Today, Shigella infects an estimated 80 to 165 million people every year, the vast majority of them in low and middle-income countries. Around 200,000 of those cases end in death, and roughly 60,000 of those deaths occur in children under the age of five. It remains one of the leading causes of moderate to severe diarrhea globally, and it is growing more dangerous as the drugs used to treat it become less reliable.
Shigella and the body it attacks
There are four main species of Shigella bacteria, each capable of causing an infection of the bowel known as shigellosis. Symptoms typically appear within one to two days of exposure, though they can take up to a week to develop, and they usually last around seven days.
The most common experience is diarrhea, which can be bloody or prolonged, accompanied by fever, stomach pain, and an persistent urge to pass stool even when nothing remains. Nausea and vomiting can also occur. In more severe cases the infection moves beyond the gut entirely, entering the bloodstream and, in some instances, leading to sepsis. In communities with poor sanitation and limited access to clean water, repeated infections in young children have been linked to stunted growth and impaired cognitive development.
Shigella spreads in ways many people do not expect
One of the characteristics that makes Shigella particularly difficult to contain is how little of the bacteria it takes to cause illness. The infection is found in fecal matter, and even minimal exposure is enough to make someone sick. It spreads through contact with an infected person, contaminated food or water, contaminated surfaces, and insects that have come into contact with infected material.
People who travel to areas with inadequate sanitation face elevated risk, as do children in school and nursery settings where outbreaks are common. Shigella can also be transmitted through sexual activity, a route that has received growing attention since around 2012 as cases among men who have sex with men have increased steadily. In the United Kingdom, reported cases in that population rose from 230 in 2022 to 432 in 2023, a trend that public health agencies have monitored with concern. Infected individuals can continue spreading the bacteria for several weeks after their own symptoms have resolved.
Shigella and the drug resistance threatening treatment
For most people, shigellosis resolves on its own within five to seven days with rest and adequate fluid intake to prevent dehydration. Antibiotics are reserved for the most severe cases, but their effectiveness is increasingly in question. Strains that are resistant to both first and second-line antibiotics have been documented and are growing in number, particularly among gay and bisexual men. The emergence of extensively drug-resistant Shigella represents a serious complication for a disease that was once considered manageable.
There is currently no approved vaccine against Shigella. Nine candidates are in clinical trials, but meaningful availability is unlikely before the 2030s. In the meantime, prevention relies on basic hygiene measures including thorough handwashing, safe food and water practices during travel, avoiding swimming while symptomatic, and taking precautions during sexual activity when either partner has been recently diagnosed. A successful vaccine would also reduce the broader dependence on antibiotics, offering a secondary benefit in the global fight against antimicrobial resistance
