Diarrheal Diseases 101

Symptoms, Causes, and Treatments for Diarrheal Diseases

little girl who is ill with diarrhea
What do you need to know about the symptoms, causes, and treatments for diarrhea?.

If you or a loved one have diarrhea, it's important to note that there are many different diarrheal diseases. What do you need to know about the symptoms, causes, and treatment for diarrhea, and what preventive measures can make a difference?


Gastrointestinal infections that cause diarrhea represent a huge public health problem in all parts of the world. In developing countries, diarrheal disease is the second-leading cause of death in children, particularly in children younger than 5 years of age.

In developed countries, including the United States, diarrheal disease is under better control but still represents a common affliction, especially among children and the elderly.

There are a number of different ways in which diarrheal diseases can be transmitted. Some can be spread from person-to-person via the fecal-oral route, with greater rates of disease found in daycare centers, hospitals and nursing homes. In addition, these diseases are frequently reported in food-borne and water-borne outbreaks.


There are two main types of infectious diarrheal disease, that differ in the mechanism underlying the symptoms:

  1. Noninflammatory: Intestinal infections, such as Cholera and Giardia, are caused by an alteration in intestinal absorption of fluids. These types of infections result in large volumes of watery diarrhea, accompanied by cramps and bloating, with mild or no fever.
  2. Inflammatory: Also known as dysentery, this kind of disease is characterized by smaller volumes of bloody diarrhea, accompanied with fever and pain. It is caused by microbes, such as Shigella and Entamoeba histolytica, that invade the colon and trigger an inflammatory immune response.


    The evaluation of diarrhea begins with a careful history. Your doctor will ask about travel, whether overseas or locally. Diseases such as Giardia may be acquired by drinking from those pristine looking streams in the mountains. Your doctor will also ask you about diet, whether you have eaten at home, at friends, or at a restaurant.

    If you have any exposure to animals, it is important to relay this, as salmonella may be transmitted by exposure to foul or reptiles. She will also perform a physical exam looking for abdominal tenderness or other signs.

    A number of laboratory tests may also be done including stool tests and blood tests. These may include:

    Stool Tests

    • Culture: A bacterial stool culture is used to identify bacterial species responsible for your infection.
    • Gram-stain: The gram stain can distinguish between the two major classes (gram-positive or gram-negative) bacteria and aid in narrowing down what kind of infection you have.
    • Ova + Parasites: A stool sample is examined for the presence of parasites and/or their eggs.
    • Fecal leukocytes: The identification of white blood cells in your stool will inform your doctor that you have an inflammatory disease.
    • Toxin and Antigen Assay: Some infections can be detected through these substances.

    Blood Tests

    • Serology: This method consists of drawing a blood sample and evaluating your antibodies to identify microbes with which you have recently been infected.
    • Culture: A blood sample is used to culture bacteria that may be responsible for your infection.


    Gastrointestinal infections can be caused by a variety of microbes, including several species of bacteria, viruses and protozoa.

    Among the more common microbes that infect the GI tract are:

    Viruses: Viruses are the most common cause of diarrhea and may include infections with:

    • Norovirus: Also known as the "cruise ship virus," norovirus is the most common cause of food-borne gastroenteritis in the United States.
    • Rotavirus: Rotavirus is the most common cause of diarrhea in children in the U.S. and is a leading cause of death of children in developing countries.
    • Adenovirus
    • Calcivirus
    • Hepatitis A: Hepatitis A an cause diarrhea which is often associated with jaundice, a yellowish discoloration of the skin.

    Bacteria: Bacterial causes of diarrhea are responsible for much of the mortality from diarrhea.

    Though a less common cause than viruses, these infections can be very serious. Bloody diarrhea is a common with these infections.

    • Salmonella enteridis: Salmonella enteritidis is one of the major reasons why we are instructed to cook poultry thoroughly and not share cutting boards used for meat and vegetables. Salmonellosis may not only occur secondary to undercooked meat, but may be transmitted on produce or acquired from handling poultry or reptiles. (This is the reason that the sale of baby turtles as pets became obsolete).
    • Escherichia coli: E coli, especially Ecoli 0157, is one of the reasons why we are advised not to eat unpasteurized diary products. It usually causes bloody diarrhea (hemorrhagic colitis).
    • Shigella species: Shigella is a common infection both in the United States and worldwide and is thought to be underdiagnosed. It often causes bloody diarrhea and is most common in children between the ages of 2 and 4.
    • Campylobacter species: Campylobacter is yet another reason why we shouldn't eat undercooked chicken or unpasteurized dairy products.
    • Vibrio species: Vibrio is one of the infectious diseases associated with eating sushi.
    • Staphylococcus aureus: Staphylococcus aureus: Staph aureus may be responsible if you have explosive diarrhea after the church picnic. Since the diarrhea is not caused by the infection but rather toxins created by the bacteria, cooking food that has been left out too long won't be effective in preventing the disease.
    • Clostridium difficilte: Clostridium difficile as a cause of diarrhea is unique in that it is often caused by antibiotic use. In fact, the risk of "C.diff" is one of the important reasons behind limiting the use of unnecessary antibiotics. C. diff is the most common cause of hospital-acquired diarrhea.
    • Yersinia: More commonly recognized as the bacteria which causes bubonic plague, Yersinia is a fairly common culpret in milk-product related infectious diarrhea.

    Protozoa: Protozoa are a type of parasite that are responsible for diarrhea both tin the U.S. and worldwide. Common protozoal causes include:

    • Giardia lamblia: Giardia is the reason we are told not to drink from those thirst-inducing mountain streams. Giardia may be present for a fairly long time until the diagnosis is made.
    • Entamoeba histolytica
    • Cryptosporidium parvum: Cryptosporidium is best known for periodic outbreaks which are often related to community swimming pools or water parks.


    Of all of these causes, half of the cases of diarrhea in children under the age of 5 years worldwide are due to Rotavirus, Calcivirus, and pathogenic E. coli.


    The main treatment approaches for diarrhea include:

    The treatments for diarrhea can be broken down into a few types of therapies. Supportive therapies such as intravenous fluids or oral rehydration and specific treatments, such as antibiotics. The use of antibiotics is not always recommended, even for bacteria diarrhea, as it can in some cases result in resistance. 

    No matter the cause of the diarrhea, it's important to correct dehydration. Dehydration is, in turn, the leading cause of fatalities from diarrhea. Symptomatic care ranging from intravenous fluids to pain relief is paramount in treatment.

    Specific treatments with anti-bacterials, anti-parasitic drugs, or antiviral medications may be used based on the organism responsible.

    Always ask your doctor about using any kind of drugs used to treat diarrheal disease. Misuse of antibiotics can result in the emergence of antibiotic-resistant superbugs, and some diarrheal drugs prevent "flushing out" of the infectious microbes and can actually do more harm than help.

    This is an important concept to understand. If your doctor is uncertain which organism is responsible for your infection she will often wait to treat you until the organism is identified. While this can be frustrating, especially if antibiotics are readily available, we know that antibiotic treatment can worsen some of these infections and even cause C. diff related diarrhea.


    An ounce of prevention is truly worth a pound of cure when it comes to many of the causes of diarrhea. Tips to help you avoid this uncomfortable illness include:

    • Practicing good personal hygiene: In developing countries, poor hygiene practice is the main reason for the high prevalence of diarrheal diseases. Use of clean water, flushed toilets and sanitary waste disposal habits in industrialized countries have limited the spread of diarrheal diseases. In addition, frequent hand washing with soap and good cooking and dining practices are important for preventing diarrheal diseases.
    • Being safe in your kitchen: Make sure all meat is cooked thoroughly. Use a meat thermometer if in doubt. Wash all fruits and vegetables, and make sure to use different cutting boards for meats and vegetables.
    • Making sure your vaccinations are up-to-date: Vaccines are available for several diarrheal diseases, including Cholera, Salmonella, Hepatitis A and Rotavirus. People traveling to other countries should find out which diseases are common in their travel destination and ask their doctor for recommended vaccines. The CDC travel website contains this information.

    When to Call Your Doctor

    Call your doctor if your diarrhea lasts more than three days, if you have a high fever, bloody stools, or prolonged vomiting, and if you develop any signs of dehydration such as thirst, dry lips, decreased urine output that is dark in color, flushed skin, sunken eyes, cramps, stiff joints, severe fatigue, irritability, and/or headache.

    Bottom Line

    Diarrhea is a significant cause of illness both in the United States and worldwide. Symptoms can vary from mild watery diarrhea to bloody diarrhea associated with severe pain. There are many different organisms which can be responsible, and it is important for your doctor to understand which of these organisms is responsible before prescribing antibiotics. The most important thing you can do is to make sure you stay hydrated. Even when specific treatments are available, supportive care is the mainstay of therapy.


    Kasper, Dennis L.., Anthony S. Fauci, and Stephen L.. Hauser. Harrison's Principles of Internal Medicine. New York: Mc Graw Hill education, 2015. Print.

    Lanata, C., Fischer-Walker, C., Olascoaga, A., Torres, C., Aryee, M., and R. Black. Global Causes of Diarrheal Disease Mortality in Children <5 Years of Age. A Systematic Review. PLoS One. 2013. 8(9):e72788.

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