Diarrhea is a condition of loose and often watery stool. Diarrhea can be caused by viruses, bacteria, and sometimes protozoa (single-celled organisms). Viral infections are the most common and the main risk is dehydration and electrolyte disturbances secondary to dehydration. Bacterial infections can also cause dehydration but may also cause high fever, bloody stools, and abdominal pain. Salmonella, Shigella, Campylobacter, and strains of E coli are all potential causes of bacterial diarrhea. Traveler’s diarrhea is another cause of bacterial diarrhea.


  • Viruses
    There are many viruses that can cause diarrhea. These are the most common infectious cause of diarrhea and are usually self-limited. The diarrhea may consist of loose or watery stools without blood or mucous. Fever may be present.
  • Bacteria
    Bacterial diarrhea can be more serious. Bacterial diarrhea can be caused by bacteria that invade the intestinal wall resulting in diarrhea that can be bloody or containing mucus. Fevers are often present and may be high. Abdominal pain is common. Salmonella, Salmonella, Campylobacter, and certain strains of E coli are the most frequently-named causes of bacteria diarrhea.
  • Protozoa
    Protozoa are single-celled organisms that can cause disease. These are commonly acquired from untreated or incompletely treated water but can be acquired from contaminated foods. Pond and streams can be contaminated with amoeba, giardia, or cryptospordium. These infections do not respond to antibiotics and may require special treatment. Diarrhea or excessive flatuluence after camping trips or drinking untreated water can be caused by protozoal illnesses.
  • Traveler’s Diarrhea
    Traveler’s diarrhea falls under bacterial diarrhea but is worth mentioning separately. Traveler’s diarrhea is the most common illness related to traveling and results from exposure to bacteria related to unclean sources of food or water. It is seldom serious but can ruin a vacation. If you are going to travel to an exotic location such as the Middle East, Africa, Mexico, Central America, or Asia, then there is a significant risk of contracting traveler’s diarrhea. It is advisable to carry antibiotics with you on such trips to treat traveler’s diarrhea should it strike. Probiotics have been suggested to reduce the risk of traveler’s diarrhea by as much as one third.


Most cases of diarrhea are uncomfortable and not serious and will resolve without treatment. However, some forms of diarrhea can be severe causing loss of water and electrolytes requiring treatment. Invasive bacteria can cause serious illness with dangerous complications and additional testing may sometimes be necessary. We can treat with anti-diarrhea medicines in most cases but these can be contraindicated if there is a serious bacterial diarrhea.


Most diarrheal illnesses are self-limited meaning they will get better on their own without treatment. The main concern is to maintain your fluid intake to prevent dehydration. Diarrhea that is persistent, contains blood or mucous, results in high fevers or significant abdominal pain may be more serious. If you have any of these symptoms, seek evaluation by a physician. In some cases, we may run tests on the stool to determine the cause of infection to help guide treatment.