As the name indicates, intestinal infections affect the gastrointestinal * tract, often causing diarrhea (dye-uh-REE-uh). Gastroenteritis (gas-tro-en-ter-EYE-tis), an inflammation of the stomach and intestines * , frequently accompanies such infections.
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What Are Intestinal Infections
Viruses, bacteria, parasites, or other pathogens (PAH-tho-jens, microscopic organisms that cause disease) can cause infections in the stomach and small and large intestines, which often lead to gastroenteritis.
When people get sick because they eat food or drink water that has been contaminated with disease-causing organisms or toxins (poisons that harm the body), it is called food poisoning or foodborne illness. Food poisoning usually affects the stomach and/or the intestines. Occasionally, however, the organism or toxin behind the illness can travel through the bloodstream and cause various symptoms in other parts of the body, such as the liver * . Some types of food poisoning can harm the fetus * carried by a pregnant woman.
Intestinal infections can be spread in many ways. Some people become infected by eating contaminated shellfish, raw or undercooked meat, or unpasteurized * dairy products, or from drinking or swimming in contaminated water. Others get sick after touching a surface (such as a kitchen counter) or bowel movement (when changing a diaper or doing laundry, for example) contaminated with an infectious organism. If they forget to wash their hands, they can carry the organism to their mouths on their hands or on food that they eat. Outbreaks of intestinal infections occur when many people eat or drink the same contaminated food or water.
Intestinal infections are very common, particularly in developing parts of the world. The World Health Organization (WHO) estimates that about 2 million children worldwide die each year from diseases that cause diarrhea. Children, the elderly, and people who have weak immune systems are most likely to contract intestinal infections.
What Bacteria Cause Intestinal Infections
or Food Poisoning?
Not all bacteria that grow in the intestines are bad. In fact, some are necessary, and many aid the body with digestion and actually help fight infection. However, other types are less welcome.
Several different strains of Salmonella (sal-muh-NEH-luh) bacteria can cause illness. The Salmonella typhi (sal-muh-NEH-luh TIE-fee) bacterium causes the most serious illness, typhoid (TIE-foyd) fever, which is common in developing countries. The National Center for Infectious Diseases reports an estimated 12.5 million cases of typhoid fever worldwide each year. In the United States, about 400 cases occur each year, most in people who have traveled to undeveloped countries. Typhoid fever spreads when people eat or drink food or water contaminated with the bacteria. People who are infected may have a high fever, headache, extreme tiredness or weakness, stomach pain, loss of appetite, and sometimes a flat, red rash. A vaccination * for travelers can help prevent typhoid fever, and antibiotics can help patients who become sick.
* gastrointestinal (gas-tro-in-TES-tih-nuhl) means having to do with the organs of the digestive system, the system that processes food. It includes the mouth, esophagus, stomach, intestines, colon, and rectum and other organs involved in digestion, including the liver and pancreas.
* intestines are the muscular tubes that food passes through during digestion after it exits the stomach.
* liver is a large organ located beneath the ribs on the right side of the body. The liver performs numerous digestive and chemical functions essential for health.
* fetus (FEE-tus) is the term for an unborn human after it is an embryo, from 9 weeks after fertilization until childbirth.
* unpasteurized (pas-CHUR-ized) refers to foods that have not undergone the process of pasteurization (pas-chu-rih-ZAY-shun), in which food is heated to a certain temperature over a period of time to kill organisms and help make the food safer to consume.
* vaccination (vak-sih-NAY-shun), also called immunization, is giving, usually by an injection, a preparation of killed or weakened germs, or a part of a germ or product it produces, to prevent or lessen the severity of a disease.
Salmonellosis (sal-muh-neh-LO-sis) is a more common but less serious illness caused by Salmonella bacteria. The U.S. Centers for Disease Control and Prevention (CDC) reports 40,000 cases in the United States each year and estimates that 20 times that number may go undiagnosed. As many as 1,000 people in the United States die from the disease each year. Eating food from contaminated animals, such as eggs, poultry, and meat, can cause salmonellosis. Symptoms start 12 to 72 hours after infection and include nausea (NAW-zee-uh), vomiting, diarrhea, fever, and stomach cramps. The disease usually runs its course in 4 to 7 days. Only infants, young children, the elderly, and people with weakened immune systems typically require treatment. (Antibiotic treatment can actually prolong the time that it takes for Salmonella bacteria to leave the body.)
Shigellosis (shih-geh-LO-sis), caused by Shigella (shih-GEH-luh) bacteria, inflames the lining of the small intestine. In the United States, about 18,000 cases are reported to the CDC each year, although the actual number may be 20 times higher. Young children are especially at risk for contracting the infection because shigellosis is transmitted through feces (FEE-seez, or bowel movements). The disease can produce complications in this age group, including seizures * .
Symptoms of shigellosis include diarrhea (sometimes with blood or mucus * ), fever, vomiting, nausea, and abdominal * cramping. Most people recover without treatment, usually within a week, although doctors may prescribe antibiotics to patients to keep the disease from spreading.
Although there are hundreds of types of Escherichia coli (commonly referred to as E coli) bacteria, only five are known to cause illness in people. In the United States, the CDC estimates that there are 73,000 cases of E. coli infection, leading to about 60 deaths, each year.
* seizures (SEE-zhurs) are sudden bursts of disorganized electrical activity that interrupt the normal functioning of the brain, often leading to uncontrolled movements of the body and sometimes a temporary change in consciousness.
* mucus (MYOO-kus) is a thick, slippery substance that lines the insides of many body parts.
* abdominal (ab-DAH-mih-nul) refers to the area of the body below the ribs and above the hips that contains the stomach, intestines, and other organs.
* strain is a subtype of an organism, such as a virus or bacterium.
An Irish immigrant cook, Mary Mallon, infected as many as 22 people in New York City with typhoid fever between 1900 and 1907. Mallon, who became known later as "Typhoid Mary," was a carrier of the disease. This means that she had no symptoms and was otherwise healthy but could spread the infection to others. (This was before antibiotics were available, which may have been able to kill the bacteria in her body.)
Although she committed no crime, city authorities held Mallon in an isolation cottage on an island in New York's East River from 1907 to 1910, and then again from 1915 (after it was discovered that she was responsible for another outbreak of typhoid fever that infected 25 people) until her death in 1938. She was confined as a threat to public health.
Many decades later, this case still raises an important and difficult question: how far should health authorities go in restricting individual rights to protect the general welfare of the public?
The most dangerous strain * of E. coli, 0157:H7, is found in the intestines of cattle. People usually become infected with the bacteria from eating undercooked ground beef, although contaminated water, unpasteurized dairy products and juices, and even fruits and vegetables can be sources of infection.
E. coli infection can cause abdominal cramps and bloody diarrhea, which last about 5 days. Most people do not need treatment, although those with weak immune systems, children, and the elderly will need to be hospitalized if they develop a serious infection.
Campylobacteriosis (kam-pee-lo-bak-teer-e-O-sis), caused by Campylobacter (kam-pee-lo-BAK-ter) bacteria, is the most common type of bacterial diarrhea in the United States. Campylobacter jejuni (je-JOO-nee) causes about 99 percent of these cases. The CDC estimates that more than 2 million people, or almost 1 percent of the U.S. population, contract the infection each year.
Campylobacter lives in animals, especially birds. Humans become infected after eating poultry that has not been thoroughly cooked. Outbreaks also have occurred after people drank contaminated water or unpasteurized milk.
Symptoms of illness begin 2 to 5 days after infection and include diarrhea (often bloody), abdominal cramping and pain, and fever. Most people recover on their own within 2 to 5 days.
Clostridium difficile infection and Clostridium perfringens food poisoning
Clostridium difficile (klos-TRIH-dee-um DIH-fih-seel) bacteria often live in the intestinal tracts of infants and young children without causing disease. In adults, however, especially the elderly, C. difficile can produce fever, watery diarrhea, abdominal pain, and loss of appetite. Risk factors for infection include taking antibiotics, a hospital stay, gastrointestinal surgery, and having another serious illness. Health care workers often spread the bacteria when they touch infected feces or contaminated surfaces, then touch patients or give them medicine without first washing their hands. C. difficile infection that causes symptoms most often occurs in people receiving long courses of antibiotics that limit the growth of the harmless bacteria that are usually present in the intestine.
Perfringens poisoning is caused by the Clostridium perfringens bacterium and is one of the most common types of food poisoning in the United States. Some C. perfringens bacteria may remain in food even after it has been cooked, then multiply when the food is cooled slowly and left at room temperature. People who eat contaminated food may develop intense abdominal cramps, diarrhea, and flatulence (excessive gas), usually within 8 to 22 hours. Most people recover from perfringens poisoning within a day or two, although symptoms can last longer in older people. Quickly refrigerating uneaten cooked food and reheating leftovers to 165 degrees or higher can help prevent perfringens poisoning.
Listeriosis (lis-teer-e-O-sis) is caused by the Listeria monocytogenes bacterium, which is found in the soil and in the intestinal tracts of animals and humans. People contract listeriosis from eating vegetables grown in contaminated soil or raw or undercooked meat, or from drinking water or unpasteurized milk and milk products.
Symptoms of illness include fever, headache, nausea, and diarrhea. The bacteria also can spread into the bloodstream or nervous system, leading to meningitis * . Pregnant women are at the greatest risk for listeriosis, and the disease can cause miscarriage * , stillbirth * , or serious illness in the newborn. Infants, older people, and people with weak immune systems are also at risk.
Toxins produced by certain strains of Staphylococcus aureus (stah-fih-lo-KAH-kus ARE-ree-us) bacteria can cause food poisoning. When people who are infected with the bacteria handle food such as meat, poultry, egg products, or dishes containing mayonnaise or cream, they may spread the bacteria to the food. The toxins build up when the food sits for long periods of time at room temperature. When a person becomes infected, symptoms come on quickly, within 2 to 8 hours, and last less than 12 hours. They include severe nausea and vomiting and sometimes abdominal cramping, diarrhea, and headache.
What Are the Major Types of Viral
Rotaviruses (RO-tuh-vy-ruh-sez) can infect people of all ages, but infants and young children are infected most often. Outbreaks occur most frequently from November to April in the United States, with about 1 million children affected each year. Of those, between 55,000 and 70,000 require hospitalization. Deaths from the illness are rare in the United States, but worldwide there are more than 600,000 deaths among children each year from rotavirus infection, according to WHO.
Rotaviruses spread when people come into contact with infected human feces. The disease is most common in daycare centers, hospital pediatric wards, and homes with young children. Symptoms appear about 2 days after infection. They include fever, vomiting, and abdominal pain, which last for 2 to 3 days, and diarrhea, which can linger for up to 8 days. Most people do not require treatment.
Enteroviruses (en-tuh-ro-VY-ruh-sez) are a group of viruses that attack the intestinal tract and cause a wide range of illnesses, including intestinal infections. People who are infected may experience mild diarrhea, vomiting, fever, and abdominal pain. Most get better on their own without treatment from a doctor.
* meningitis (meh-nin-JY-tis) is an inflammation of the meninges, the membranes that surround the brain and the spinal cord. Meningitis is most often caused by infection with a virus or a bacterium.
* miscarriage is the ending of a pregnancy through the death of the embryo or fetus before birth.
* stillbirth is the birth of a dead fetus.
The hepatitis (heh-puh-TIE-tis) A virus is found in water contaminated by sewage, in shellfish from contaminated water, and in fruits and vegetables grown in contaminated soil. The virus can spread when people eat or drink contaminated food or water or from person to person during sexual intercourse. Infected people who handle or prepare food can transmit the virus if they touch food after going to the bathroom and not washing their hands thoroughly.
Some people with hepatitis A infection show no signs of illness, but those who do may experience fever, extreme tiredness, loss of appetite, nausea, and vomiting. The patient's liver enlarges and the skin may appear yellowish, a condition known as jaundice * . The disease can lead to permanent liver damage, although this is rare. Symptoms appear 2 to 4 weeks after infection and may last several weeks to months. A vaccine is available to protect people at high risk from hepatitis A infection.
Other Causes of Intestinal Infection
Parasites are the culprits behind many intestinal infections. Amebiasis (ah-mih-BYE-uh-sis), caused by Entamoeba histolytica (en-tuh-ME-ba his-toh-LIH-tih-kuh); giardiasis (jee-ar-DYE-uh-sis), the work of the Giardia intestinalis protozoa * ; and infection with Cyclospora cayetanensis (syklo-SPORE-uh kye-uh-tuh-NIN-sis) are all common parasitic infections that lead to intestinal symptoms such as cramping and diarrhea.
How Do Doctors Diagnose Intestinal Infections
and Food Poisoning?
Many cases of intestinal infection are so mild that they go unnoticed. Others get better without the patient ever seeing a doctor. The symptoms of gastroenteritis, namely nausea, vomiting, abdominal pain, diarrhea, and loss of appetite, are common to many intestinal infections and some other diseases as well. When patients go to a doctor, they may be diagnosed with an intestinal infection or food poisoning based on a physical exam and their history of symptoms and food intake.
Mild cases likely will not require any laboratory tests, and the actual cause of the infection may never be known. In more severe cases of illness, however, doctors may collect samples of a bowel movement to examine under the microscope and send to be cultured * in order to identify the organism involved.
How Are Intestinal Infections Treated?
Most intestinal infections do not require treatment, and patients get better on their own. People with diarrhea and other signs of intestinal infections should talk to their doctors if the symptoms do not clear up in a few days.
* jaundice (JON-dis) is a yellowing of the skin, and sometimes the whites of the eyes, caused by a buildup in the body of bilirubin, a chemical produced in and released by the liver. An increase in bilirubin may indicate disease of the liver or certain blood disorders.
* protozoa (pro-tuh-ZOH-uh) are single-celled microorganisms (tiny organisms), some of which are capable of causing disease in humans.
* cultured (KUL-churd) means subjected to a test in which a sample of fluid or tissue from the body is placed in a dish containing material that supports the growth of certain organisms. Typically, within days the organisms will grow and can be identified.
* dehydration (dee-hi-DRAY-shun) is a condition in which the body is depleted of water, usually caused by excessive and unreplaced loss of body fluids, such as through sweating, vomiting, or diarrhea.
In most cases, patients can remain at home and maintain a relatively normal schedule. Children sometimes need to stay out of daycare until the illness resolves. While they recover, patients must be sure to drink plenty of fluids to avoid dehydration * . Doctors also advise that they avoid anti-diarrhea medicine because it may keep the infectious agent in the body longer. More severe cases of intestinal infections sometimes require hospitalization so patients can receive intravenous fluids * , antibiotics, or other treatment. In most cases, people should feel better within days to a week, although it may be several more weeks before their gastrointestinal tracts recover completely.
Can Intestinal Infections Cause Other
In otherwise healthy people, intestinal infections rarely cause complications. Mild dehydration is the most common consequence. Infants and the elderly are most at risk for severe dehydration. For people with weak immune systems (such as patients undergoing chemotherapy or people with HIV or AIDS * ), the infectious agent may spread throughout the body, causing widespread disease and even death. In infants and young children, cases of long-lasting illness occasionally lead to malnutrition or a failure to grow properly because the infections interfere with their nourishment.
More specific complications from intestinal infections vary. Salmonellosis and shigellosis can lead to Reiter (RYE-ter) syndrome, which is characterized by joint pain, eye inflammation, and difficulty and pain with urination. Campylobacter infection may trigger Guillain-Barre (GEE-yan bah-RAY) syndrome, a nerve inflammation that causes muscle weakness or paralysis * . Salmonella infection can result in arthritis * , meningitis, brain abscesses * , and bone infections. Escherichia coli can cause hemolytic uremic syndrome, a disease that can progress to kidney * failure and severe anemia * .
How Can People Prevent Intestinal Infections?
Practicing good hygiene is the best way to prevent intestinal infection. That includes frequently and thoroughly washing hands, especially after changing diapers, after going to the bathroom, and before handling food or eating.
Travelers who plan to visit developing countries need to make sure they have any recommended vaccinations (such as the one for typhoid fever) before they leave. Once there, experts advise that they drink only bottled water and avoid eating raw fruits and vegetables, food from street vendors, and unpasteurized dairy products. To be safe, all food should be eaten steaming hot.
In the United States, a rotavirus vaccine used in the late 1990s caused bowel problems in some infants and is no longer recommended. Work continues on the development of a new vaccine.
* intravenous (in-tra-VEE-nus) fluids are fluids injected directly into a vein.
* AIDS, or acquired immunodeficiency (ih-myoo-no-dih-FIH-shen-see) syndrome, is an infection that severely weakens the immune system; it is caused by the human immunodeficiency virus (HIV).
* paralysis (pah-RAH-luh-sis) is the loss or impairment of the ability to move some part of the body.
* arthritis (ar-THRY-tis) refers to any of several disorders characterized by inflammation of the joints.
* abscesses (AB-seh-sez) are localized or walled off accumulations of pus caused by infection that can occur anywhere within the body.
* kidney is one of the pair of organs that filter blood and remove waste products and excess water from the body in the form of urine.
* anemia (uh-NEE-me-uh) is a blood condition in which there is a decreased amount of oxygen-carrying hemoglobin in the blood and, usually, fewer than normal numbers of red blood cells.
U.S. Centers for Disease Control and Prevention (CDC), 1600 Clifton
Road, Atlanta, GA 30333. The CDC is the U.S. government
authority for information about infectious and other diseases. It has
fact sheets on many types of intestinal infections on its website.
U.S. Food and Drug Administration, Center for Food Safety and Applied
Nutrition (CFSAN), 5100 Paint Branch Parkway, College Park, MD 20740.
CFSAN has an online "Bad Bug Book" that gives facts and
figures on various foodborne illnesses.