Gastrointestinal, or GI, infections can be viral, bacterial, or parasitic infections that affect the digestive tract. The most common symptoms include nausea, vomiting, abdominal pain, diarrhea, and fevers. Severe infections can cause more serious symptoms, such as bloody stool or bloody vomiting, chest pain, irregular heartbeat, headaches, confusion, changes in vision, weakness, muscle paralysis, or hallucinations. Some parasitic infections, which are more rare in the United States, may only present with weight loss.
Dehydration is a potential short-term complication of GI infections that cause diarrhea, but some GI infections also have potential long-term consequences. Certain types of infections can cause ongoing abdominal pain, diarrhea, constipation, bloating, or cramping. Other long-term symptoms can involve the skin, nerves, muscles, eyes, heart, or joints.
Salmonella infection is the most common bacterial infection causing gastroenteritis and leads to the highest number of hospitalizations and deaths in the United States. Foods commonly contaminated by Salmonella include poultry, fresh produce, eggs (contamination of the shell), meats such as beef and pork, and dairy products.
Shigella is bacteria frequently found in water polluted with human feces. Infection with Shigella is called shigellosis or bacillary dysentery.
Campylobacter infections are common bacterial infections that can lead to short- and long-term illness. Long-term complications can include joint inflammation and nerve damage that leads to muscle weakness. Campylobacter can contaminate poultry, dairy products, produce, and meats such as pork and beef.
Escherichia coli (E. coli)
There are many different types of E. coli that can cause severe bacterial infections. In addition to GI symptoms, E. coli infections can injure the kidneys, blood vessels, and nervous system. E. coli can come from uncooked beef, unprocessed milk, contaminated produce, and water contaminated with human or animal feces.
Clostridium difficile (C. difficile)
C. difficile, or C. diff, infection is a bacterial infection usually contracted in hospitals or healthcare institutions, but up to 30 percent of the population is now colonized by these bacteria. To be colonized by bacteria means that the bacteria live together with the host without causing disease. Elderly and immunocompromised patients are at highest risk for infection.
Listeria infections are bacterial infections that most significantly impact the very young, very old, and immunocompromised patients, as well as pregnant women. Listeria can cause more severe symptoms in vulnerable populations, which may include infections of the brain. Listeria in pregnant women can cause miscarriage or premature birth. Listeria can come from deli meats, undercooked pork and poultry, produce, and seafood.
Staphylococcus aureus is bacteria that can be found on, or colonizes, human skin, and can cause infection in cuts, sores, noses, and throats. It is also a food-borne bacteria that can cause severe diarrhea, or "food poisoning." It can spread in foods, such as meat, poultry, eggs, produce, bakery products, and dairy products. This is the classic toxin-producing bacteria that causes diarrheal illness after a picnic.
Helicobacter pylori (H. pylori)
H. pylori are spiral-shaped bacteria that likely spread through unclean food, water, or eating utensils, and contact with an infected person's saliva or other body fluids. Infection from H. pylori does not always cause gastroenteritis, but can lead to peptic ulcers, and is closely associated with stomach cancer.
Norovirus and Rotavirus
Both of these viruses can cause GI infections. Rotavirus usually infects children more than adults, and norovirus is more common in adults. Norovirus is frequently associated with large outbreaks in restaurants or catered events, hospitals, schools, and cruise ships. These viruses are spread from person to person.
Adenovirus is the second most common cause of GI infections in children, behind rotavirus. It can also cause conjunctivitis (inflammation and infection of part of the eye), bladder infections, rashes, and respiratory illness.
Hepatitis A is a virus that can cause injury to the liver and is most commonly transmitted through contamination of food or water by human feces. GI symptoms of hepatitis A infections may be mild at first, but can become more severe. There is an immunization for hepatitis A for those traveling outside of the United States to a region where this infection is more common.
Cryptosporidium and Cyclospora
These are two parasites that can cause symptoms of gastroenteritis, as well as infections of the liver, bile ducts, gallbladder, and pancreas. Cryptosporidium is carried by cattle and typically infects immunocompromised patients through contaminated water, produce, and unpasteurized milk. Cyclospora can be transmitted by fresh produce such as berries and basil, as well as contaminated water sources. These infections don't usually last long, but in some cases, they persist for weeks or even months.
Toxoplasma gondii (T. gondii)
Toxoplasma is a parasite that can only reproduce in cats and is passed in their feces. It causes infections when people ingest the parasitic cysts through contaminated soil, food, or water. This can happen changing a cat's litter box. Infection is particularly dangerous for pregnant women and immunocompromised patients. The most common foods associated with Toxoplasma contamination are beef, produce, poultry, dairy, and deli meats.
This parasite can infect, colonize, or set up permanent residence, and reproduce in the small intestine. Individuals with immunoglobulin deficiencies and low gastric acidity are especially at risk for this type of infection. Giardia lamblia is usually transmitted by drinking contaminated water.