Intestine Infection (Small, Large Bowels) Causes, Symptoms, Treatment

Intestinal infections are frequent occurrence for most people. From what we refer to as the “stomach flu” to food poisoning, bugs that enter mainly with food and water often cause infections of the small and large intestine (bowels). Most of the time these infections are acute and quickly resolve within a few days. However, some intestinal infections can be severe and even lead to death if not properly treated and managed.

What are intestinal infections?

An intestinal infection is inflammation and tissue damage of the small intestine and/or large intestine that occurs with infectious agents, like viruses, bacteria, protozoa or even fungi. Sometimes the toxins of these agents may cause inflammation on its own. Intestinal infections are common, second only to upper respiratory infections like the common cold and seasonal flu. Sometimes an intestinal infection can accompany these respiratory tract infections.

Enteritis and Colitis

Inflammation of the small intestine is known as enteritis while inflammation of the large intestine is known as colitis. When both the small and large intestine are inflamed at the same time then it is known as enterocolitis. The stomach lies next to the small intestine and if both the stomach and small intestine are inflamed together then the condition is referred to as gastroenteritis.

  • Enteritis = small intestine
  • Colitis = large intestine
  • Enterocolitis = small + large intestines
  • Gastroenteritis = stomach + small intestine

Read more on enteritis and types of colitis.

Signs and Symptoms

There are several symptoms that arise when the small and/or large intestines become inflamed. This includes:

  • Diarrhea
  • Abdominal pain or cramps
  • Excessive flatulence
  • Nausea and vomiting
  • Fever
  • Loss of appetite

Nutritional deficiencies may arise with small intestine infections. This is due to inflammation of the small intestine which hampersĀ  the absorption of nutrients (malabsorption). Dehydration is a common complication that arises as a result of vomiting and diarrhea. The signs and symptoms of dehydration may therefore be present.

Causes of Intestinal Infections

Although infections are not the only cause of enteritis or colitis, it is by far the most common. Autoimmune diseases, radiation exposure and injury to the bowels are some of the other non-infectious causes of intestinal infections. Infectious enteritis and/or colitis are caused by viruses, bacteria, protozoa and in some rare cases by fungi. These infectious agents are mainly spread by contaminated food and water. Parasitic worms, also known as intestinal helminths, may cause infestations of the intestines.

Read more on human intestinal worms.


The most common bacteria to cause intestinal infections are:

  • Escherichia coli (including both enterohemorrhagic E coli [EHEC] and enteroinvasive E coli [EIEC])
  • Shigella spp
  • Salmonella spp
  • Campylobacter spp
  • Yersinia spp

The toxins of some of these bacteria may enter the body through contaminated food and water and also cause enteritis or colitis even without the causative bacteria being present.


The most common viruses to cause intestnal infections are:

  • Rotavirus
  • Calciviruses, especially norovirus
  • Adenovirus
  • Astrovirus

Other viruses like the cytomegalovirus (CMV) can also cause intestinal infections but these are rare.


Single-celled parasites known as protozoa may also be responsible for intesinal infections. Entamoeba histolytica is a common protozoan to cause an intestinal infection which is known as entamoebiasis or simply as amoebiasis. Giardiasis is another common protozoal infection of the intestines caused by Giardia intestinalis.


There are several fungal species that may be found in the gut in small numbers and some are considered part of the normal intestinal flora. Fungal infections of the intestines are rare. Overgrowth of yeasts, like Candida species, may occur secondary to bacterial infections. An yeast infection of the intestine may possibly occur with severe weakening of the immune system as is seen with AIDS

How are intestinal infections spread?

There are several different ways in which intestinal infections are spread. It varies based on the cause of the infection. These infectious agents (viruses, bacteria and protozoa) most commonly enter the body through the mouth to then reach the gastrointestinal tract.

  • Secretions: Saliva and mucus may spread the infectious agent when these secretions are airborne by coughing or sneezing, or transmitted through sharing of food and utensils.
  • Fecal particles: Infectious agents may be found in the feces of infected individuals. These fecal particles may enter the mouth of an infected person through direct contact or via food/water.
  • Food and water: Contamination of food and water with the infectious agents is a very common method of spread. Secretions and fecal particles may also be the source of the food/water contamination.

Treatment of Intestinal Infections

An intestinal infection must be assessed by a medical professional so that the appropriate treatment can be prescribed. This may involve diagnostic investigations like blood tests and a stool analysis. The treatment of intestinal infections depends on a host of factors such as the cause of the infection, presence of complications and individual immunity. Acute viral infections may not require any treatment beyond supportive measures to prevent complications like dehydration.

The following treatment may be necessary depending on the type and severity of the intestinal infection:

  • Antibiotics to eradicate the causative bacteria of the intestinal infection.
  • Antiviral drugs for viral intestinal infections that do not resolve spontaneously but is rarely needed.
  • Antiemetics to suppress nausea and ease vomiting to some degree.
  • Antidiarrheal agents to suppress diarrhea although it should not be a first choice of treatment.
  • Acetaminophen, aspirin or ibuprofen for pain and fever.
  • Intravenous (IV) fluid administration for rehydration in moderate to severe dehydration.

Home Remedies

  • Bed rest is important to overcome the infection and prevent additional strain on the body. It can also help with minimizing further water and electrolyte loss as well as spreading the causative infectious agent.
  • Rehydration with an oral rehydration solution (ORS) to prevent and manage mild to moderate dehydration. IV hydration may be necessary in severe dehydration or where vomiting prevents oral rehydration.
  • Probiotic supplements containing spores of microbes like Lactobacillus spp and Saccharomyces boulardii may help restore the normal intestinal flora (“good” bowel microbes).
  • Nutritious meals that are bland but balanced are important to prevent nutrient deficiencies. Solid foods should not be stopped if diarrhea is present unless vomiting prevents eating.

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