Diarrhea caused by viral infection differs from diarrhea caused by bacteria in terms of symptoms, treatment, and causes. It is important to determine which kind you have in order to receive proper treatment. Your medical provider will be able to differentiate between viral and bacterial diarrhea.

Viral gastroenteritis, which is a viral infection of the stomach and the small intestine, is the most common cause of acute diarrhea worldwide. Symptoms of viral gastroenteritis typically last only 48-72 hours and include nausea, vomiting, and abdominal cramps. Unlike bacterial enterocolitis, patients with viral gastroenteritis usually do not have blood or pus in their stools and have little to no fever.

Viral gastroenteritis can occur in a sporadic form in a single individual or in an epidemic form among groups of individuals. Sporadic diarrhea is likely caused by several different viruses and is believed to be spread by person-to-person contact. The most common cause of epidemic diarrhea, such as on cruise ships, is infection with a family of viruses known as caliciviruses, with norovirus being the most common. Caliciviruses are transmitted by food that is contaminated by sick food handlers or by person-to-person contact.

Bacterial enterocolitis, on the other hand, is caused by disease-causing bacteria that usually invade the small intestines and colon, resulting in inflammation. Symptoms of bacterial enterocolitis include signs of inflammation such as blood or pus in the stool, fever, abdominal tenderness, abdominal pain, and diarrhea. Common bacteria that cause acute enterocolitis include Campylobacter jejuni, Shigella, Salmonella, and EPEC. These bacteria are usually acquired by drinking contaminated water or eating contaminated foods such as vegetables, poultry, and dairy products.

Enterocolitis caused by the bacterium Clostridium difficile (C-Diff) is unusual because it often occurs as a result of antibiotic treatment. Clostridium difficile is also the most common nosocomial infection (infection acquired while in the hospital) that causes diarrhea. Unfortunately, C. difficile infection is also increasing among individuals who have neither taken antibiotics nor been in the hospital.

The mortality and morbidity of diarrhea can vary depending on the region and population. Acute diarrhea remains a significant cause of childhood mortality globally, with diarrhea being the second most common cause of death in children younger than 5 years. Despite a progressive reduction in global diarrheal disease mortality over the past two decades, diarrhea morbidity has slightly increased worldwide compared to previous reports.

In the United States, an average of 369 diarrhea-associated deaths per year occurred among children aged 1-59 months during 1992-1998 and 2005-2006. The majority of diarrhea-associated infant deaths were reported in 2005-2007, with 86% of deaths occurring among low-birthweight (< 2500 g) infants.

In countries with high rates of diarrhea, poverty adds an enormous additional burden, and the long-term consequences of enteric infections, diarrhea, and malnutrition are devastating.

Factors such as sex and age can also play a role in the incidence and severity of diarrhea. For example, females have a higher incidence of Campylobacter species infections and hemolytic uremic syndrome (HUS). Viral diarrhea is most common in young children, with rotavirus and adenovirus being particularly prevalent in children younger than 2 years. Very young children are particularly susceptible to dehydration and nutrient malabsorption as a result of diarrhea. Age and nutritional status are important factors in determining the severity and duration of diarrhea, with younger children at a higher risk for severe dehydration and a prolonged course of diarrhea.