Gastroenteritis is inflammation of the gastrointestinal tract that involves both the stomach and small intestine. Gastroenteritis results in combination of diarrhea, vomiting, and abdominal pain and cramping. Globally, most cases are caused different viruses for all age groups. Less common causes include other bacteria or their toxins and parasites.

Bacterial Gastroenteritis

Bacterial gastroenteritis is caused by food poisoning (If food becomes contaminated with bacteria and remains at room temperature for a period of several hours, the bacteria multiply and increases the risk of infection in those who consume the food). Some foods commonly associated with illness include raw or undercooked meat, poultry, seafood, and eggs; raw sprouts; unpasteurized milk and soft cheeses; and fruit and vegetable juices.

Viral Gastroenteritis

Rotavirus, norovirus, adenovirus, and astrovirus are known to cause viral gastroenteritis. Rotavirus is the most common cause of gastroenteritis in children. Rotavirus is a less common cause in adults due to acquired immunity. Norovirus is the cause of about 10% of cases in children. Norovirus is the leading cause of gastroenteritis among adults. These localized epidemics typically occur when groups of people spend time in close physical proximity to each other. People may remain infectious even after their diarrhea has ended.

Parasitic Gastroenteritis

A number of protozoans can cause gastroenteritis. It occurs more commonly in persons who have traveled to areas with high prevalence, children who attend day care, men who have sex with men, and following disasters.

Transmission may occur via consumption of contaminated water, or when people share personal objects. In places with wet and dry seasons, water quality typically worsens. In areas of the world with seasons, infections are more common in the winter. Bottle-feeding of babies with improperly sanitized bottles is a significant cause on a global scale.

There are also a number of non-infectious causes of inflammation of the gastrointestinal tract. Some of the more common include medications, certain foods such as lactose (in those who are intolerant), and gluten (in those with celiac disease).