Shigella infection, also called shigellosis, is a highly contagious bacterial illness that causes diarrhea (often bloody), fever, and stomach cramps. The CDC estimates roughly 450,000 cases occur in the United States each year, making it the third most common bacterial gut infection in the country. Symptoms typically appear one to two days after exposure and last about seven days.
How Shigella Spreads
Shigella bacteria spread through the fecal-oral route, which means the bacteria from an infected person’s stool end up being swallowed by someone else. This sounds extreme, but it happens easily. Tiny amounts of bacteria on hands after using the bathroom, on contaminated food prepared by someone who didn’t wash their hands, in recreational water like pools or lakes, or on shared surfaces like toys in a daycare center can all carry enough bacteria to cause illness.
What makes Shigella particularly contagious is that the infectious dose is extremely small. Swallowing just a few hundred bacteria is enough to make you sick, far fewer than most other foodborne pathogens require. This is why it spreads so readily in settings where people are in close contact: childcare facilities, households with young children, and crowded living environments. People can also spread the bacteria for weeks after their symptoms resolve if they don’t wash their hands carefully.
Symptoms and What to Expect
Most people with shigellosis experience diarrhea that can be bloody or last more than three days, fever, stomach pain, and a persistent feeling of needing to use the bathroom even when nothing comes out. That last symptom, called tenesmus, is one of the more uncomfortable hallmarks of the infection. Some people also experience nausea and vomiting, though these are less central to the illness.
Symptoms generally begin one to two days after you’ve been exposed. For most people, the worst of it passes within five to seven days without any specific treatment. However, the diarrhea can be severe enough to cause dehydration, especially in young children and older adults, which is the most immediate concern during the illness.
Who Is Most at Risk
Children under five are the group most frequently affected by Shigella, largely because of how easily it spreads in daycare settings and because young children are less consistent with handwashing. International travelers visiting regions with limited sanitation infrastructure also face higher risk, as do people in any congregate living situation where hygiene resources may be limited.
People with weakened immune systems tend to experience more severe and prolonged illness. For this group, the infection is more likely to require antibiotics and carries a higher risk of complications.
How It Is Diagnosed
Doctors diagnose shigellosis by testing a stool sample. The traditional method is a stool culture, where the sample is placed on special growth plates in a lab to see whether Shigella bacteria grow. This process typically takes 24 to 48 hours. Molecular tests that detect Shigella’s genetic material can identify the bacteria faster and with greater sensitivity than culture alone, and many labs now use these as a first step. If bacteria do grow in culture, the lab can then test which antibiotics will work against that particular strain, which has become increasingly important given rising resistance.
Treatment and Recovery
Most people with shigellosis recover on their own in five to seven days with nothing more than fluids and rest. Staying well hydrated is the single most important thing you can do during the illness, since frequent diarrhea pulls fluid and electrolytes out of your body quickly. Oral rehydration solutions, water, and clear broths all help.
For severe cases, particularly when there’s high fever, bloody diarrhea that isn’t improving, or the patient has a compromised immune system, doctors may prescribe antibiotics to shorten the illness and reduce the chance of spreading it to others. The two most commonly recommended oral options are ciprofloxacin and azithromycin.
One thing to avoid: anti-diarrheal medications like loperamide. These can slow the movement of your gut and potentially make the infection worse by keeping the bacteria inside longer.
The Growing Problem of Drug Resistance
Antibiotic resistance in Shigella is a serious and worsening issue. Of the roughly 450,000 annual U.S. cases, an estimated 242,000 involve strains that are resistant to at least one antibiotic. More alarmingly, extensively drug-resistant (XDR) strains have emerged rapidly. In 2015, essentially zero percent of reported Shigella infections were XDR. By 2022, about 5% were.
XDR Shigella strains resist all of the antibiotics doctors would normally reach for, including ciprofloxacin, azithromycin, ceftriaxone, trimethoprim-sulfamethoxazole, and ampicillin. That leaves very few treatment options, and the CDC currently has no formal guidelines for treating these infections. Doctors managing XDR cases typically consult infectious disease specialists to determine the best approach, which may involve less common antibiotics that these strains haven’t yet developed resistance to. This resistance trend makes prevention even more critical.
How to Prevent Shigella Infection
Because Shigella spreads so easily with so few bacteria, handwashing is the most effective defense. Washing with soap and water (not just sanitizer) after using the bathroom, after changing diapers, and before preparing or eating food covers the most important moments of transmission. For young children, supervised handwashing makes a real difference.
In daycare and early education settings, prevention also means regularly cleaning and disinfecting toys, surfaces, and shared objects. During outbreaks, facilities should increase the frequency of this cleaning and make sure all staff and parents know how the bacteria spread. Shigellosis is a reportable condition in every U.S. state, meaning confirmed cases get flagged to local health departments so they can identify and contain outbreaks before they grow.
Possible Complications
Most Shigella infections resolve without lasting effects, but complications can occur. Some people develop reactive arthritis weeks after the gut infection has cleared. This causes joint pain, eye irritation, and painful urination, and it can persist for months or even become chronic. It’s triggered by the immune system’s response to the infection rather than by the bacteria themselves still being present.
In rare cases, particularly with certain Shigella strains, the infection can lead to hemolytic uremic syndrome, a condition where red blood cells are destroyed and the kidneys begin to fail. This is most common in young children. Seizures can also occur in children with high fevers during the acute illness, though these are typically brief and don’t cause long-term harm. Severe dehydration from prolonged diarrhea remains the most common complication across all age groups and is largely preventable with adequate fluid intake.