Causes of Gastroenteritis

Most often, a person will develop gastroenteritis after contact with an infected person or due to ingestion of contaminated food (such as shellfish harvested from contaminated sources) or water. Unhygienic practices, like inadequate washing of hands after using the restroom, also aid the spread of the disease.

Gastroenteritis is caused by viruses and bacteria, and less often by parasites and protozoa. Sometimes, one may develop gastroenteritis if he or she consumes food items, which irritate the intestines. 

Viral gastroenteritis 

Viral gastroenteritis¹is caused by four major categories of viruses:

1. Rotavirus
2. Norovirus
3. Adenovirus
4. Astrovirus

Rotavirus: This is the most common cause of severe debilitating diarrhea in young children, sometimes requiring hospitalization. Infected adults are usually unaffected, but can spread the illness.

Norovirus: Older children and adults are usually affected by noroviruses. This virus is responsible for epidemics and seasonal outbreaks of gastroenteritis.² If a person experienced muscle ache, fatigue, and headache in addition to the usual symptoms of diarrhea and vomiting, it is more likely that he or she has norovirus gastroenteritis.

Adenovirus: This virus affects children under the age of 2 years. Symptoms of infection with adenoviruses take a longer time to appear.

Astrovirus: Infections with astroviruses are more common in the winter months and in young children.

Bacterial gastroenteritis

Bacterial gastroenteritis³is less common than viral gastroenteritis. Common bacteria that cause gastroenteritis are:

1. Campylobacter and Salmonella spp
2. Shigella spp
3. Escherichia coli

Campylobacter and Salmonella spp.: These are the most common causes of bacterial diarrhea. The infection is generally acquired from undercooked eggs and dairy products.⁴  Also, if the pet dogs or cats have campylobacter infection, then a person acquire the infection from them.

Shigella spp: Infection with Shigella spp. tends to be more severe in children and the elderly.

Escherichia coli: Several variants of this bacteria cause gastroenteritis. The most common type of infection with E. coli occurs when a person consumes undercooked ground beef, unpasteurized milk and juice, and contaminated water.⁷ Person-to-person contact also occurs in settings such as daycare centers and nurseries. A variant of E. coli causes a watery diarrhea, commonly referred to as ‘travelers’ diarrhea’.⁵

Other bacteria such as Clostridium perfringens, Staphylococcus aureus and Bacillus cereus produce symptoms by releasing toxins into contaminated food.

Parasites and protozoa

Parasites and protozoa are less frequently responsible for gastroenteritis. One of these microorganisms can be picked up from the swimming pool or by drinking contaminated water. Some common parasites, which cause gastroenteritis are as follows:³

Giardia: Infection resulting from Giardia is more common in colder climates and spreads from person-to-person or through contaminated drinking water.

Cryptosporidium spp.: Infection with this parasite can be lethal in people with a weakened immune system.

Entamoeba spp.: Infection with Entamoeba histolytica, which is less common in USA, results in a bloody diarrhea.

• Consumption of drinking water contaminated with heavy metals such as arsenic, lead, and mercury.

• Inability to tolerate the lactose in milk products (lactose intolerance).⁶

• Side-effects of medications such as antacids, antibiotics, chemotherapy drugs and laxatives.

Next page: Signs and symptoms of gastroenteritis

Written by: Healthplus24 team
Date last updated: April 01, 2012