The Cleveland Clinic defines acute or sudden onset, diarrhea as loose watery stool that occurs more times a day than normal for less than 14 days. Adults in the United States experience at least 99 million episodes of acute diarrhea each year. The small intestine and large intestine, also known as the colon, function to absorb excess fluids from the partially digested food material. Acute diarrhea usually occurs due to infectious organisms which interfere with the absorptive process of the intestines.
Viral Infections
Viral infections as the most common cause of diarrhea in the United States, according to the Cleveland Clinic. Rotavirus infection causes severe diarrhea, especially in children. Other symptoms include vomiting, fever and abdominal pain. The symptoms of a rotavirus infection typically continue for three to eight days, according to the Centers for Disease Control and Prevention, or CDC.
Other viruses that cause infectious acute diarrhea include noroviruses, also known as Norwalk-like viruses and adenoviruses. These viral infections cause acute gastroenteritis which result in diarrhea, vomiting and abdominal pain. Viruses that cause acute diarrhea spread through the fecal-oral route usually through food contaminated by improper hand washing.
Bacterial Infections
Bacterial infections can also cause sudden onset diarrhea. Since these types of infections usually spread through food contaminated either by improper hand washing or improper cooking, they are often referred to as food poisoning.
Some bacteria, such as Shigells and E. coli, destroy cells in the intestines causing diarrhea. Other bacteria, including Salmonella, Campylobacter jejuni, and Yersinia enterocolitica, cause mild to severe inflammation in the lining of the intestines, as described by the Cleveland Clinic. Bacteria such as B. cereus, S. aureus and Clostridium perfringens, produce toxins that cause the intestines to secrete more fluids and electrolytes than they absorb, resulting in sudden diarrhea.
Parasites
Parasites ingested in contaminated food or water settle in the digestive tract and penetrate the walls of the intestines causing inflammation that causes sudden diarrhea. The most common parasite infections include Giardia, Entamoeba histolytica and Cryptosporidia.
Food Intolerance
Food intolerance occurs when an individual cannot tolerate certain substances found in foods. Lactose intolerance, a common condition, describes the inability to digest the sugar known as lactose found in milk and milk products, according to the National Digestive Diseases Information Clearinghouse. Because the body cannot absorb lactose, it produces an enzyme known as lactase to break lactose into simple sugars it can absorb. Lactose intolerance occurs due to a lactase deficiency. Food intolerances cause diarrhea because the sugar remains in the stool, retaining water with it, as described by the Merck Manual.
