By: Candess Zona-Mendola

Outbreaks of illness are concerning for everyone. In moments that an outbreak has hit too close to home, say your favorite restaurant or your child’s school, the concern sometimes turns into fear and anxiety. In times like this, the best tool is to be educated and how you can prevent infection or the spread.

What is an Outbreak?

The word “outbreak” brings a lot of frightening mental images for some people. Some believe the mention of an outbreak is a mass infection situation. But outbreaks can be small. A mass infection situation is called a pandemic, and is defined by the Centers for Disease Control and Prevention as “an epidemic that has spread over several countries or continents, usually affecting a large number of people.”

The basic definition of an outbreak is: when two or more people become infected with a pathogen of similar origin (source) and the pathogens found in the victims are closely related in genetic matching to each other. Outbreaks can consist of two people or hundreds. Typically, outbreaks are also limited to a specific, usually limited, geological area. There are outbreaks in the United States that span the entire country, but they are usually clustered to certain areas.

An outbreak of Shigella comes on quickly, as the bacteria easily spreads form person to person. As symptoms can vary from mild to severe, many do not report their illnesses. This makes it difficult to identify and stop an outbreak, especially of this kind.

What is Shigella? How Common is it?

Shigella, or rather its infection Shigellosis, is one of the more common foodborne illnesses. The Centers for Disease Control and Prevention estimate that approximately 500,000 people per year are infected with some species of Shigella. Despite is great quantity in the United States, it rarely causes epidemics like it does in developing countries. This is not to be underestimated though. Shigella can be deadly, especially in those that are part of the high risk group for foodborne illness – like young children, the elderly, pregnant women, and those who are immunocompromised. Shigella also does not have a specific time of year it peaks, like E. coli or Salmonella. Trends for the infection are also not on the decline.

For more information on recent Shigella outbreaks, you can visit our posts here and here.

I Think I Have Shigella. How Would I Know?

The best way to determine if you have Shigella is to see your physician and obtain a stool test. You can simply ask your doctor to order this test. Some individuals, when infected with Shigella bacteria, may not show any signs or symptoms of the infection. The bacteria, however, will continue to live in their intestinal tract until the body’s immune system has completely destroyed it. For those who do show symptoms, they will typically have the following:

  • watery diarrhea
  • sometimes bloody diarrhea
  • nausea
  • vomiting
  • abdominal cramping
  • mucus in stool
  • sometimes a fever
  • tenesmus (a painful feeling f needing to pass stool even when the bowels are empty)

Those who are infected and show symptoms will do so within one to three days after ingesting infected food or drink. Usually, healthy adults will recover within five days to a week. But those who are in the high risk group may have longer, more severe infections.

If you are exhibiting any of the symptoms mentioned above, medical attention is recommended. Shigella infections may have long-term complications. Early medical attention may help reduce the likelihood of complication.

Shigellosis Complications

Shigella, like E. coli, emits a toxin when ingested and digested into the intestinal tract. This toxin can cause an array of complications, including the following according to the Centers for Disease Control and Prevention:

  • Post-infectious arthritis.About 2% of persons who are infected with Shigella flexneri later develop pains in their joints, irritation of the eyes, and painful urination. This is called post-infectious arthritis. It can last for months or years, and can lead to chronic arthritis. Post-infectious arthritis is caused by a reaction to Shigella infection that happens only in people who are genetically predisposed to it.”
  • “Blood stream infections.Although rare, blood stream infections are caused either by Shigella organisms or by other germs in the gut that get into the bloodstream when the lining of the intestines is damaged during shigellosis. Blood stream infections are most common among patients with weakened immune systems, such as those with HIV, cancer, or severe malnutrition.”
  • “Seizures.Generalized seizures have been reported occasionally among young children with shigellosis, and usually resolve without treatment. Children who experience seizures while infected with Shigella typically have a high fever or abnormal blood electrolytes (salts), but it is not well understood why the seizures occur.” and
  • “Hemolytic-uremic syndrome or HUS.HUS occurs when bacteria enter the digestive system and produce a toxin that destroys red blood cells. Patients with HUS often have bloody diarrhea. HUS is only associated with Shiga-toxin producing Shigella, which is found most commonly in Shigella dysenteriae.”


Preventing infection and spread of Shigella is easy. Hand washing is among the best tools anyone can use to prevent the spread of infection. Those who are sick who work in or attend schools, nursing homes, daycares, food service, or other places where many people gather together, should remain home until their symptoms have passed.



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American Academy of Pediatrics. Red Book: Report of the Committee on Infectious Diseases. 2012. 645-647.