Foodborne and waterborne illnesses are common, but often unrecognized. Many illnesses carried by food or water are particularly common in the developing world, due to poor sanitation, polluted water, and lack of refrigeration. However, about 20 percent of all cases of diarrhea in the United States are believed to be caused by foodborne or waterborne illness, resulting in approximately 76 million illnesses, 300,000 hospitalizations, and 5,000 deaths yearly.

The most common symptom is diarrhea, defined as six or more soft or water-like stools daily. Episodes vary considerably. For example, severe bacterial infections may cause diarrhea every 30 minutes. The primary concerns in patients with diarrhea are dehydration, electrolyte imbalances, and kidney failure, among other disorders.

Rarely, food or waterborne illness may be associated with more severe complications, such as anemia, seizures, and blood, liver, heart, or lung disease.

Complete avoidance of foodborne illness may not be possible. However, risk can be minimized through proper cooking and handling to avoid cross-contamination. Risk is further reduced by avoiding foods of animal origin. However, certain plant foods may also be contaminated during production, processing, or handling.

Foodborne and Waterborne Illness: Types of Infections

• Salmonella. This widespread infection has two main types: typhoid fever and non-typhoid infection. Salmonella usually occurs due to undercooked poultry, contamination of foods or cooking surfaces, and raw or undercooked eggs (including egg-containing products, such as mayonnaise and custards). Milk, meat, and produce, such as alfalfa sprouts, may also transmit disease.
  
  Typhoid fever often results in fever, abdominal pain, swollen liver and spleen, diarrhea (which may be bloody), and skin rash. Non-typhoid salmonella infection often results in nausea, vomiting, diarrhea, and fever, and is the most common cause of foodborne illness in the United States.
• Campylobacter. The second most common cause of foodborne illness in the United States is campylobacter. Like salmonella, it is a common resident of the chicken's intestinal tract and can contaminate chicken meat during processing. Undercooked poultry and contamination of other foods are the most likely sources. As much as 60 percent of retail poultry products throughout the world and up to 85 percent in the United States are contaminated with campylobacter. Bloody diarrhea may occur.
• Shigella. The third most common cause of foodborne illness in the United States is shigella. It causes bloody diarrhea and may result in severe blood disorders. It spreads through food, water, or person-to-person contact, and is common in nursing homes and daycare settings.
• Cryptosporidium. This parasite is transmitted through ingestion of its eggs in contaminated water, or exposure to cows and their manure. It can also contaminate produce and unpasteurized milk. Cryptosporidium can also be found in pools and spas and can spread from person to person.
• Escherichia coli. The E. coli O157:H7 strain is spread most often through undercooked hamburger. Unpasteurized juice and raw produce contaminated by cattle manure may also be sources. It may cause bloody diarrhea and can lead to severe blood disorders. Like salmonella, it usually occurs in the summer and fall.
• Yersinia. This bacterial infection typically comes from undercooked pork, unpasteurized milk, or contaminated water.
• Vibrio cholerae. This bacterial infection results in a severe diarrhea. It occasionally occurs along the Gulf Coast from contaminated water. Another type of vibrio infection, Vibrio parahaemolyticus, is due to ingestion of contaminated shellfish.
• Cyclospora. This infection occurs due to produce that has been exposed to contaminated water and from person-to-person contact. It may cause diarrhea and other symptoms, such as fatigue.
• Bacillus cereus. This infection can occur in under-heated foods, such as rice, and is often found in food left under heating lamps. It can cause severe vomiting and diarrhea.
• Staphylococcus aureus. Common sources include contaminated salads, eggs, meat, and dairy products that have been prepared and left at room temperature.
• Viral infections. Norovirus is the most common viral cause of diarrhea. It occurs in families and among persons living in other close quarters, such as cruise ships, and can be transmitted through the air by contaminated hands and other objects.
• Entamoeba histolytica. Infection is most common in tropical regions. In addition to causing painful, severe diarrhea with blood and mucus, the infection may also cause liver abscess and ulcers on the anus. It can be transmitted sexually, as well as by consumption of contaminated water.
• Listeria monocytogenes. Listeria is fatal in nearly 20 percent of cases. It can cause meningitis and is most common in infants and elderly persons. This organism is the basis for the warning to pregnant women not to consume unpasteurized soft cheeses, particularly from Latin America. Raw hot dogs and deli meats are also high-risk foods.
• Clostridium botulinum. This bacterium causes a life-threatening paralysis called botulism. Infection can occur as a result of home canning, fish fermentation, and extended use of food warmers.
• Toxoplasma. This infection may occur through ingestion of raw beef or lamb or by contamination from cat feces (e.g., in infrequently cleaned litter boxes and gardens). Infection with toxoplasmosis during pregnancy is dangerous to the fetus.
• Trichinosis. This disease is caused by ingestion of undercooked pork and wild game, such as bear. Cattle and horse meat can also be contaminated. Trichinosis rarely causes diarrhea, but may cause eye, heart, or brain symptoms. It is now rare in the United States, due to regulatory controls on the feeding of pigs.
• Brucellosis. Brucellosis is found in contaminated dairy and meat products, commonly from Latin America. Brucellosis may result in high fevers, meningitis, bone infection, and rashes.
• Tapeworms. Tapeworms can result from eating raw fish, beef, and pork. One type of tapeworm can travel to the brain and may result in seizures.
• Prions. Prions are abnormal proteins that cause brain disease, such as bovine spongiform encephalopathy ("mad cow disease"). The risk to humans has been reduced by regulations for livestock feeding and processing.

Foodborne and Waterborne Illness: Risk Factors, Diagnosis, Prevention and Treatment

Risk Factors

• Age: Young children are the most likely to develop diarrhea. Elderly persons are also at higher risk.
• Medications, including antibiotics and antacids
• Food traditions: Intentionally undercooked or raw meats and fish (e.g., steak tartare, sushi, and oysters) increase the risk of foodborne illness.
• Hygiene: The spread of disease is more common in environments where clean water is not available, infected food handlers expose others to infections, or hand washing is not possible (or may be improperly done, as in the case of children at daycare facilities).

Diagnosis

• A detailed medical history and a physical examination are essential.
• Laboratory testing may include stool studies and blood tests, including blood cultures.

Prevention and Treatment

Prevention is the most effective way to limit food and waterborne illness. Essential to prevention efforts are clean drinking water, restaurant and meat inspection, temperature monitoring, appropriate sewage processing, monitoring of public waterways for contamination, and public education on proper hygiene and food handling.

All patients with suspected foodborne illness should be instructed in proper hand-washing techniques to protect others with whom they are in contact. Diagnosis of foodborne illness generally requires notification of the Department of Public Health.

Most episodes of diarrhea will resolve without specific treatment. In severe cases, antibiotics and intravenous fluids may be needed. Additionally, a vaccine is available for typhoid fever and hepatitis A.

Foodborne and Waterborne Illness: Nutritional ConsiderationsFoods of animal origin, particularly meat and eggs, are the most common causes of foodborne illness. Investigators working with the Food and Drug Administration (FDA) have discovered that resistant strains of salmonella are common in retail ground meats, including ground chicken, beef, turkey, and pork.

Raw oysters and other shellfish may be a source of vibrio infection if they come from contaminated waters, particularly the Gulf of Mexico. The U.S. Department of Agriculture (USDA) listed eggborne infection with salmonella as an important public health problem in the United States in 2000, and it continues to be a problem due to products that contain undercooked eggs, such as mayonnaise, ice cream, and custards.

In addition, dairy farms are a potential source of listeria infection, which is responsible for 28 percent of U.S. food-related deaths every year. Other studies have found that dairy farms are also a source salmonella, E. coli, and yersinia infections.

Produce may become contaminated with fecal pathogens during planting, irrigating, harvesting, processing, and shipping, or through contaminated water.

Food service establishments can be a frequent source of foodborne infection, although the risk is also present in homes and any other setting that allows for lapses in preparing, cooking, and storing food. A 2005 survey of food service personnel found that more than 50 percent did not always wear gloves while touching ready-to-eat foods; almost 25 percent did not follow appropriate hand-washing guidelines; more than 33 percent did not always change gloves between handling raw meat and ready-to-eat foods; and more than 50 percent did not use a thermometer to check food temperatures. All these precautions should be used in any setting where food is prepared.

The Centers for Disease Control, FDA, and USDA have established the Foodborne Diseases Active Surveillance Network (FoodNet). FoodNet's purpose is to monitor trends in foodborne diseases and assess which diseases are attributable to specific foods and settings in the United States. You can visit FoodNet at www.cdc.gov/foodnet.