Infectious colitis is an inflammatory condition caused by bacteria, a virus, or a parasite. It can cause diarrhea and other symptoms. Treatment will depend on the cause.

Infectious colitis causes symptoms similar to inflammatory bowel disease (IBD), including rectal pain, increased urgency to pass stool, and bloody mucus discharge from the anus.

Several pathogens may cause this acute form of diarrhea, including viruses, parasites, and bacteria.

This article reviews what infectious colitis is, its types, symptoms, causes, and more.

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Colitis is inflammation of the colon, which is the part of the intestines where stool forms.

Colitis can cause several symptoms, including:

  • abdominal pain
  • bloating
  • nausea
  • urgent diarrhea

Infectious colitis is a type of colitis resulting from viruses, bacteria, or parasites.

It is generally an acute illness that will clear within about 7 days, with or without treatment. More severe cases can last for several weeks.

Common types of colitis and their causes include:

  • Viral colitis: Norovirus, rotavirus, adenovirus, and cytomegalovirus.
  • Bacterial colitis: Campylobacter jejuni, Salmonella, Shigella, Escherichia coli, Yersinia enterocolitica, Clostridium difficile, and Mycobacterium tuberculosis.
  • Parasitic colitis: Entamoeba histolytica
  • Sexually transmitted colitis: HIV, gonorrhea, chlamydia, herpes simplex 1 and 2, and syphilis.

While different types of colitis can cause similar symptoms, the underlying cause may affect treatment.

Infectious colitis can cause symptoms similar to those of IBD and gastroenteritis, such as:

  • watery or bloody diarrhea
  • vomiting
  • abdominal pain
  • nausea
  • fevers
  • appetite loss
  • weight loss

Most people who develop infectious colitis do so after coming into contact with contaminated food or water.

People may be at higher risk of contracting infectious colitis if they:

  • travel to foreign countries
  • stay in a hospital
  • take antibiotics
  • have close contact with an infected person

Bacterial infections account for about 47% of all cases. Common bacterial causes in the United States include Salmonella and Clostridium difficile, also known as Clostridioides difficile.

Living with certain medical conditions, such as sickle cell anemia or hemolytic anemia, or taking certain medications, such as immunosuppressors, puts a person at a higher risk of Salmonella infection.

Other possible bacterial causes include:

  • Campylobacter
  • Shigella
  • E. coli
  • Yersinia

Less commonly, amebic (parasitic) and viral infections can cause colitis.

During an exam, a doctor will ask about a person’s symptoms. They may also ask about possible exposure to known risk factors, such as a recent hospital stay or travel abroad.

They will likely run bacteria cultures of stool samples to determine whether the underlying cause of symptoms is bacterial in origin.

The doctor may also order additional testing, such as CT scans, a colonoscopy, tissue biopsies, and fecal cultures, to rule out other colitis causes.

Treatment may vary depending on the cause. Antibiotics can help treat bacterial colitis. However, antibiotics are inappropriate for children because of the risk of hemolytic uremic syndrome.

For C. diff, doctors recommend antibiotic treatment for most people, especially if they are immunosuppressed.

Most people with mild forms of colitis do not need treatment. Infections typically clear on their own.

A person may develop dehydration due to fluid loss from diarrhea.

Other complications depend on the underlying pathogen causing the infection. Possible complications include:

Most cases of infectious colitis will clear in about 7 days. However, in severe cases, it may take several weeks before the infection clears.

In some cases, a person can contract the infection again shortly after infection — for example, about 1 in 6 people with C. diff get it again within the following 2–8 weeks. Washing hands regularly, sanitizing surfaces, and avoiding people with the infection can help prevent a recurrence.

In addition to antibiotic treatment, in some cases, a fecal transplant may be necessary.

Below are some common questions on infectious colitis.

How serious is infectious colitis and how long does it last?

Most people start to feel better in about 7 days. In severe cases, it can take several weeks before the infection passes.

How do you get a colitis infection?

The most common form of transmission is through contaminated food or water.

What is the treatment for infectious colitis?

Treatments may involve letting the infection run its course or providing fluids and antibiotics. Some people may need fluids in a hospital setting.

What is the difference between infectious and ulcerative colitis?

Ulcerative colitis is a type of chronic inflammatory bowel disease. It results from an abnormal immune response where the immune system attacks healthy colon tissue.

Infectious colitis results from an infectious agent that causes inflammation in the colon. It is generally self-limiting and clears within a few days.

What is the difference between infectious colitis and gastroenteritis?

Gastroenteritis occurs due to a viral or bacterial infection, commonly rotavirus. It is common in children. Similar to infectious colitis, it causes intestinal inflammation, but it also causes inflammation in the stomach.

Another main difference is that gastroenteritis typically does not cause bloody diarrhea.

Infectious colitis is inflammation of the intestines resulting from an underlying bacterial, viral, or parasitic infection. Bacteria are the most common cause of infectious colitis.

Generally, the condition does not require medical treatment.

Some people may contract the infection again. Regular handwashing and avoiding those with an infection can help prevent reinfection.