Overview and Risk Factors
Foodborne and waterborne illnesses are common, but often unrecognized. They cause an estimated 76 million illnesses, 300,000 hospitalizations, and 5,000 deaths yearly in the United States.1,2 The most prominent symptom is acute diarrhea, but the associated dehydration may lead to electrolyte irregularities, acute renal failure, and encephalopathy. Rarely, food or waterborne illness may be associated with prolonged or more severe complications, such as anemia, shock, hemolytic-uremic syndrome, spontaneous abortion, seizures, and liver, heart, or lung disease. 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, developed countries are by no means exempt. About 20% of all US diarrheal episodes are believed to be caused by foodborne or waterborne illness.3
This chapter focuses mainly on acute diarrheal illnesses, but also includes information on prions and other rare diseases that are part of the full scope of foodborne and waterborne illness.
Risk factors for specific pathogens are presented below.
Age. Young children are the most likely to have acute diarrhea. Institutionalized elderly persons are also at higher risk.
Medications. Antibiotic use alters the normal gut flora, and H2-receptor blockers or other medications may increase gastric pH. Both of these factors increase susceptibility to foodborne illness.
Food traditions. Intentionally undercooked or raw meats and fish (eg, steak tartare, sushi, and oysters) increase the risk of foodborne illness. This is a particular concern in patients with advanced liver disease or immunocompromised states, such as T-cell immunodeficiencies.
Hygiene. The spread of disease is facilitated by environments where unpolluted water is not available, infected food handlers expose others to pathogens, or sanitary hand washing is not possible (or may be improperly done, as in the case of children at daycare facilities).
A detailed history to assess changes in the patient's bowel pattern and temporal relationships with exposures to food, antibiotics, sick persons, or travel (including hiking and camping) is important. The history may help determine whether the condition is likely to be self-limited or requires treatment. In addition, the history points toward likely causative organisms that may be candidates for testing. For example, a history of blood or mucus in the diarrhea warrants stool examination. Laboratory evaluation usually includes culture, leukocyte count, fecal occult blood testing, and possibly screening for ova and parasites.
Acute diarrhea diagnosis in the clinical setting is based on an increased frequency and looser consistency of stools. Diarrhea is defined as 6 or more soft or waterlike daily stools, although episodes vary considerably. Severe bacterial cases may cause diarrhea every 30 minutes. Viruses, especially noroviruses, cause the majority of gastroenteritis cases. The major clinical decision for severe or persistent diarrhea is whether supportive therapy (ie, oral or intravenous rehydration therapy for volume depletion) is sufficient, or whether pathogen-focused antibiotics are required. Note: Antibiotics are rarely needed.
Irritable bowel syndrome, inflammatory bowel disease, malabsorption syndromes (eg, celiac sprue, gluten, and other food intolerances), and hyperthyroidism should be considered in the differential if the diarrhea does not resolve within 1 to 2 weeks.
Salmonella. This widespread foodborne illness occurs in 2 main types: typhoid fever and nontyphoidal infection. Typhoid fever classically presents systemically with fever, hepatomegaly, and splenomegaly, and a tender abdomen, but it may also include rash (ie, a classic "rose spot" skin lesion) and diarrhea or constipation. Nontyphoidal salmonella infection typically presents with nausea, vomiting, diarrhea, and fever, and is the most common cause of foodborne gastroenteritis in the United States. Illness usually occurs due to undercooked poultry, cross-contamination of other foods or cooking surfaces, and raw or undercooked eggs (including egg-containing products, such as mayonnaise and custards, left at room temperature).
Milk, meat, and fecally contaminated fresh produce, such as alfalfa sprouts, may also transmit disease, as can pet reptiles. Disease occurs more commonly in the summer and fall. Particularly susceptible are individuals with inflammatory bowel disease, lymphomas, and altered bowel flora (eg, due to antibiotics). Bloody diarrhea may occur.
Carriers of Salmonella typhi (eg, the infamous cook "Typhoid Mary" in early 20th century New York) occasionally cause typhoid fever epidemics.
Campylobacter. The second most common cause of foodborne illness in the United States is Campylobacter jejuni. Undercooked poultry and cross-contamination of other foods are the most likely sources. On average, 60% of retail poultry products throughout the world,4 and up to 88% in the United States,5 are contaminated with campylobacter. Bloody diarrhea may also occur with campylobacter infection.
Shigella. The third most common cause of foodborne illness in the United States, Shigella flexneri, is a highly infectious (an inoculum of just 10 organisms can cause infection) and pathogenic bacterium that often causes bloody diarrhea. Other complications include hemolytic uremic syndrome and thrombotic thrombocytopenic purpura. It spreads through food, water, or person-to-person contact, and is common in nursing homes and daycare settings.
Cryptosporidium parvum. This parasite is transmitted through ingestion of C parvum eggs in contaminated or inadequately filtered water, or exposure to cows and their manure. In addition to being a common water contaminant, it can contaminate produce and unpasteurized milk. Cryptosporidium is a common infectious agent in pools and spas and can also spread from person to person.6
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 the hemolytic uremic syndrome and thrombotic thrombocytopenic purpura. Like salmonella, it usually occurs in the summer and fall. Other more common E coli strains may also cause diarrheal illness, such as enterohemmorhagic and enteroinvasive E coli.
Yersinia enterocolitica. This bacterial infection typically comes from undercooked pork, unpasteurized milk, or contaminated water.
Vibrio cholerae. This bacterial infection results in a secretory diarrhea. It occasionally occurs along the Gulf Coast from contaminated water. Vibrio parahaemolyticus infection is due to ingestion of contaminated shellfish.
Cyclospora cayetanensis. A parasitic infection acquired from produce exposed to contaminated water and from person-to-person contact, it may cause prolonged diarrhea and systemic symptoms, such as fatigue.
Bacillus cereus. A bacterium that can multiply in underheated foods, such as rice, it is often found in food left under heating lamps. B cereus produces toxins that typically cause rapid-onset vomiting and may also cause diarrhea.
Staphylococcus aureus. The toxins produced by S aureus may cause symptoms similar to those caused by B cereus. Common sources include contaminated salads, eggs, meat, and dairy products that have been prepared and left at room temperature.
Clostridium perfringens. Found in contaminated meat and poultry, it produces toxins after ingestion.
Viral gastroenteritis. Norovirus is the most common viral cause of gastroenteritis and may cause vomiting and explosive diarrhea. It occurs in families and among persons living in other close quarters, such as cruise ships, and can be transmitted through the air and via the fecal-oral route. Rotavirus, adenovirus, and astrovirus are other viral causes of intestinal illness.
Giardia lamblia. This very common intestinal parasite is often found in mountain streams due to fecal contamination by beavers and bears. It is also spread through food and person-to-person (fecal-oral) contact.
Entamoeba histolytica. An infection occurring worldwide, it is prevalent in tropical regions. In addition to causing painful profuse diarrhea with blood and mucus, amoebic infection may also cause ulcers on the anus and liver abscesses with systemic symptoms. It can be transmitted sexually, as well as by consumption of contaminated water.
Hepatitis A. This virus can be contracted through water, produce (eg, strawberries and cantaloupe), milk, and raw shellfish. Spread usually occurs through cross-contamination by an infected food handler at any point from the farm to the plate. Fecal-oral transmission may also occur through sexual contact.
Listeria monocytogenes causes listeriosis and is fatal in nearly 20% of cases. The most common manifestations include bacteremia and meningitis, particularly in infants and the elderly. 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. Less commonly, one may develop gastroenteritis related to listeriosis.
Clostridium botulinum causes a life-threatening paralysis and may result from home canning, fish fermentation, and extended use of food warmers.
Toxoplasma gondii infection may occur through ingestion of raw beef or lamb or through cross-contamination from cat feces (eg, in infrequently cleaned litter boxes and gardens). Infection is generally self-limited and asymptomatic, except in immunocompromised patients. However, primary infection with toxoplasmosis during pregnancy is dangerous to the fetus. Immunocompetent individuals may develop a mononucleosis-like syndrome. With T-cell immunodeficiencies, such as HIV or those in heart transplant recipients, the organism often causes brain, retinal, lung, and muscle lesions.
Trichinosis. This disease is caused by ingestion of encysted larvae in undercooked pork and wild carnivorous game, such as bear. Cattle and horse meat can be cross-contaminated. Trichinosis rarely causes diarrhea, but may cause ocular, cardiac, neurologic, and muscular symptoms such as muscle swelling and pain after larval migration. It is now rare in the United States, due to regulatory controls on the feeding of pigs.
Echinococcus. This parasite may be ingested in water contaminated by wild and domestic canines (eg, foxes and wolves), particularly in the Middle East, Greece, Africa, and Asia. Cysts may infect the liver and lungs.
Brucellosis. Brucellosis, particularly B abortus, B melitensis,and B suis, is found in contaminated dairy and meat products, commonly from Latin America. Brucellosis may result in high fevers, septicemia, septic arthritis, meningitis, osteomyelitis, and rashes.
Tapeworms can result from eating raw fish, beef, and pork. Cysticercosis occurs through raw pork ingestion. Migration to the brain may result in seizures, and migration to the skin and liver may also occur. In rare instances, fish tapeworms may cause pernicious anemia due to vitamin B12 malabsorption. Beef tapeworms are asymptomatic.
Fish toxins, such as ciguatera and scombroid, can become concentrated in larger fish. Cigutera is associated with neurologic/cardiovascular complications, while histamine-related complications are associated with scombroid. In addition, tetrodotoxin in puffer fish is often fatal due to multiorgan system collapse.
Prions are abnormal proteins that cause slowly progressive spongiform encephalopathies, including Creutzfeldt-Jakob disease and bovine spongiform encephalopathy (BSE, or "mad cow disease"). The latter disease emerged in the mid-1990s in Great Britain, presumably due to the practice of feeding cattle the remains of other ruminants, particularly sheep (sheep are susceptible to a similar spongiform encephalopathy called scrapie). Evidence suggests that human cases of variant Creutzfeldt-Jakob disease have been due to prion transmission through consumption of infected cattle.7 The risk to humans has been reduced by regulations for livestock feeding and processing that helps prevent ingestion of concentrated neural material (ie, brain and spinal cord). Similar diseases occur in other animals, such as chronic wasting disease in deer and elk.
Prevention and Treatment
Prevention is the most effective way to limit the morbidity and mortality associated with 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. The public should be cautioned about foods presenting particular risk and given instruction in proper food handling and preparation.
Vaccines are available for hepatitis A and typhoid fever.
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 acute diarrhea episodes are self-limited. Oral or intravenous rehydration therapy may be needed, and an antimotility drug (eg, loperamide) may be useful in viral diarrhea. Some outcomes may be improved or the disease course shortened through antibiotic treatment, but only when a specific diagnosis is suspected.
Salmonella (nontyphoidal) is usually self-limited, although antibiotic treatment should be used in very sick individuals, such as those with concurrent immunocompromised states or vascular disease or at the extremes of age.
Typhoid fever may be multidrug resistant. Fluoroquinolones or third-generation cephalosporins are generally effective, although resistance to many antibiotics has emerged.
Campylobacter may be treated with antibiotics, which may shorten the duration of illness. Typically, fluoroquinolones, erythromycin, and tetracycline are effective. However, many studies have verified growing resistance to fluoroquinolones.8
Shigella, like salmonella and campylobacter, is treated with antibiotics when patients are very sick, immunocompromised, or a risk to public health (ie, food handlers, day care attendees, hospital workers). Antibiotic choice depends on the age of the patient and resistance patterns. Typical antibiotics are trimethoprim-sulfamethoxazole, azithromycin, cephalosporins, and fluoroquinolones.
Cryptosporidiosis treatment is rarely necessary in immunocompetent persons.
E coli (O157:H7) should generally not be treated with antibiotics, as lack of efficacy is well-documented and treatment has been linked with a higher incidence of hemolytic uremic syndrome. Other E coli infections may require supportive therapy. Traveler's diarrhea, often caused by E coli, usually responds to a fluoroquinolone given for 1 to 3 days.
Yersinia requires antibiotics in complicated illness only.
For Vibrio infections, rehydration therapy is essential due to the risk of severe diarrhea resulting in volume loss and shock. Antibiotics may shorten the course of diarrhea and vibrio excretion, and may be used as a therapy adjunct. Doxycycline, tetracycline, and fluoroquinolones are possible choices. Macrolides are commonly used for children.
Listeria should be treated promptly with intravenous antibiotics, such as penicillin G or trimethoprim-sulfamethoxazole. A 2-week treatment is generally prescribed, except in immunocompromised patients, for whom longer courses are required. Gentamicin can be added for severe infections, once its potential toxicity is considered.
Botulism may be treated with an antitoxin, and antibiotics may be used, although they have uncertain efficacy. Intense monitoring in a hospital is required. Other treatments (eg, wound debridement) may be considered if indicated.
Toxoplasma gondii infection should be treated in pregnant and immunocompromised patients, or in the presence of severe or prolonged symptoms. Pyrimethamine and sulfadiazine (folic acid antagonists) are the drugs of choice, along with folinic acid to prevent sulfadiazine-associated bone marrow suppression.
Cyclospora can be treated with trimethoprim and sulfamethoxazole.
Tapeworms can be prevented by cooking or freezing meat prior to ingestion and by avoiding cross-contamination. Praziquantel is the treatment of choice for active disease.
Amoeba and giardia may be treated with metronidazole.
Echinococcus calls for surgical excision ("marsupialization") after cyst injection with hypertonic saline by surgeons familiar with this procedure. Oral albendazole may be provided as well.
Trichinosis can usually be prevented by freezing meat. For individuals who consume pork or other at-risk meats, thorough cooking also kills these pathogens. Treatment is not usually necessary, but mebendazole and albendazole are generally effective. Symptomatic treatment of pain and fever and systemic steroids are often helpful.
Foods of animal origin, particularly meat and eggs, are most often implicated in cases of foodborne illness.9 Scientists at the CDC's Foodborne and Diarrheal Diseases Branch have observed that foodborne illness starts near the bottom of the food chain in the form of contamination of animal feed with Salmonella enterica.10 Other investigators working with the Food and Drug Administration's (FDA) Division of Animal and Food Microbiology Office have documented that resistant strains of salmonella are common in retail ground meats, including ground chicken, beef, turkey, and pork.11
Consumers may believe that choosing white meat in place of red meat will reduce their risk for foodborne infection. However, a multistate investigation linked an outbreak of listeria to processed turkey meat, resulting in a recall of 16 million pounds of the product.12 Eating chicken in restaurants has been noted as the most common cause of infection with campylobacter, a bacterium that is a common cause of gastroenteritis in the United States.13
Raw oysters and other shellfish eaten by approximately 10% of adults each year may be a source of vibrio vulnificus gastroenteritis if harvested from contaminated waters, particularly the Gulf of Mexico.14 The US Department of Agriculture's (USDA) Food Safety and Inspection Service listed eggborne infection with Salmonella enteritidis as an important public health problem in the United States in 2000.15 However, the problem appears to be ongoing, partly as a result of food-handling practices and specifically due to ingestion of products containing undercooked eggs, such as mayonnaise, ice cream, and custards.
In addition, better food handling will not prevent infections passed in intact eggs.16 The USDA's Animal Disease Research Unit has found that dairy farms are a potential source of Listeria monocytogenes, a zoonotic foodborne pathogen that is responsible for 28% of U.S. food-related deaths every year.17 Other studies have found that dairy farms are also a reservoir for multidrug-resistant Salmonella typhimurium,18 E coli (O157:H7),19 and Yersinia enterocolitica,20 as well as other pathogenic organisms.21
Produce may become contaminated with fecal pathogens during planting, irrigating, harvesting, processing, and shipping, or through contaminated water.22
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 poor temperature control in preparing, cooking, and storing food.9 A 2005 survey of food-service personnel found that more than 50% did not always wear gloves while touching ready-to-eat foods; almost 25% did not follow appropriate hand-washing guidelines; more than 33% did not always change gloves between handling raw meat and ready-to-eat foods; and more than 50% did not use a thermometer to check food temperatures.23 All these precautions should be used in any setting where food is prepared.
The CDC, FDA and USDA have established the Foodborne Diseases Active Surveillance Network (FoodNet) as a component of the CDC's Emerging Infections Program (EIP). FoodNet's purpose is to monitor trends in foodborne diseases, determine the societal burden caused by these diseases, and assess which diseases are attributable to specific foods and settings in the United States. Data listed on FoodNet's Web site clearly indicate that the routine practice of using antibiotics in animal feed selects for the development of antimicrobial resistance.24 The site lists U.S. farms and dairies in violation of guidelines to avoid antibiotic use. Tracing the origin of contaminated meat by FoodNet is complicated by the fact that a single hamburger might contain meat from many cows and that the beef is handled at multiple facilities.1 These factors make it extremely difficult to identify the origin of contamination. Extensive research into flash gamma irradiation has shown effective eradication of bacterial contamination. However, low public acceptance has resulted in slow implementation of this process.25
What to Tell the Family
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.
In the case of immunocompromised patients, ingestion of raw fish and raw meat is associated with a higher risk of foodborne illnesses. Patients with chronic liver disease should be strongly encouraged to avoid raw shellfish, including oysters, clams, and shrimp.
1. Kuehn BM. Surveillance and coordination key to reducing foodborne illness. JAMA. 2005;294:2683-2684.
2. Centers for Disease Control and Prevention. Diagnosis and Management of Foodborne Illness. A Primer for Physicians and Other Health Care Professionals. MMWR. 2004;53(RR-4):1-33.
3. Imhoff B, Morse D, Shiferaw B, et al. Burden of self-reported acute diarrheal illness in FoodNet surveillance areas, 1998-1999. Clin Infect Dis. 2004;38(suppl 3):S219-S226.
4. Cui S, Ge B, Zheng J, Meng J. Prevalence and antimicrobial resistance of Campylobacter spp. and Salmonella serovars in organic chickens from Maryland retail stores. Appl Environ Microbiol. 2005;71:4108-4111.
5. Smith KE, Besser JM, Hedberg CW, et al. Quinolone-resistant Campylobacter jejuni infections in Minnesota, 1992-1998. N Engl J Med. 1999;340:1525-1532.
6. Centers for Disease Control and Prevention. Surveillance for waterborne-disease outbreaks associated with recreational water in the United States, 2001-2002. MMWR. 2004;53(SS-8):1-22.
7. Collinge J. Variant Creutzfeldt-Jakob disease. Lancet. 1999;354:317-323.
8. Gupta A, Nelson JM, Barrett TJ, et al. Antimicrobial resistance among Campylobacter strains, United States, 1997-2001. Emerg Infect Dis. 2004;10:1102-1109.
9. Todd EC. Epidemiology of foodborne diseases: a worldwide review. World Health Stat Q. 1997;50:30-50.
13. Friedman CR, Hoekstra RM, Samuel M, et al. Risk factors for sporadic Campylobacter infection in the United States: A case-control study in FoodNet sites. Clin Infect Dis. 2004;38(suppl 3):S285-S296.
18. Villar RG, Macek MD, Simons S, et al. Investigation of multidrug-resistant Salmonella serotype typhimurium DT104 infections linked to raw-milk cheese in Washington State. JAMA. 1999;281:1811-1816.
19. Murinda SE, Nguyen LT, Ivey SJ, et al. Prevalence and molecular characterization of Escherichia coli O157:H7 in bulk tank milk and fecal samples from cull cows: a 12-month survey of dairy farms in east Tennessee. J. Food Prot. 2002;65:752-759.
21. Altekruse SF, Timbo BB, Mowbray JC, Bean NH, Potter ME. Cheese-associated outbreaks of human illness in the United States, 1973 to 1992: sanitary manufacturing practices protect consumers. J Food Prot. 1998;61:1405-1407.
24. Centers for Disease Control and Prevention. FoodNet--Foodborne Diseases Active Surveillance Network. Available at: http://www.cdc.gov/foodnet/. Accessed December 26, 2005.
25. Oldfield EC III. Emerging foodborne pathogens: keeping your patients and your families safe. Rev Gastroenterol Disord. 2001;1:177-186.