The stomach flu is caused by various infectious agents including parasites, bacteria and viruses. Individuals contract the stomach flu by eating or ingesting the infectious agent. Common sources include animal products, poorly washed produce and contaminated water. An individual can spread the infection from one person to another by failing to practice proper hand-washing techniques after a bowel movement. Each type of stomach flu creates about the same symptoms with minimal variations, including differences in duration.
Viral Stomach Flu
When the stomach flu is caused by a virus, it is often called viral gastroenteritis. The Centers for Disease Control and Prevention states that noroviruses, rotaviruses and adenoviruses are some of the most common viruses responsible for the stomach flu. This type of stomach infection causes watery diarrhea, abdominal cramps, nausea, vomiting and sometimes a fever, according to MayoClinic.com. This stomach flu is easily spread from an infected person to another individual and through food and water. Typical cases of viral gastroenteritis last one or two days, but the illness can last up to 10 days. Some individuals experience an improvement in symptoms but still have some abdominal discomfort after the illness seems to have passed. This includes going 24 hours without any noticeable symptoms but then experiencing a bout of stomach cramping or diarrhea.
Bacterial Stomach Flu
MedlinePlus suggests that bacterial gastroenteritis can affect one person or a group of people who have consumed the same contaminated food or drink. Animal products, like meat or poultry, come in contact with bacteria from the intestines of the animal during slaughter and preparation. When these items are not cooked thoroughly, the result can be infection. Common types of bacteria that cause the stomach flu include salmonella, E. coli and shigella. Symptoms of bacterial stomach flu include abdominal cramps, stomach pain, bloody stools, diarrhea, appetite reduction, nausea and vomiting. Some bacteria are more likely than others to cause severe diarrhea or bloody stools, including salmonella and E. coli. Bacterial gastroenteritis can last several hours or a few days. MedlinePlus recommends seeking medical treatment after five days of diarrhea or 12 hours of vomiting, especially in small children.
Parasitic Stomach Flu
The most common parasites responsible for diarrhea, abdominal cramping and nausea, as indicated by the National Digestive Diseases Information Clearinghouse, include Gardia lamblia, Entamoeba histolytica and cryptosporidium. Depending on the parasite, other symptoms can occur, such as foul-smelling diarrhea that is oily, excess gas and weight loss, according to MayoClinic.com. These parasites enter the body through water or food, like other sources of the stomach flu. Symptoms may take one or two weeks to appear after exposure. They can last between two and six weeks without treatment. More severe parasitic infection may require medications to kill the organism and stop the symptoms of the stomach flu.
