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E. coli

   Information from CDC

Currently, there are four recognized classes of enterovirulent E. coli (collectively referred to as the EEC group) that cause gastroenteritis in humans. Among these is the enterohemorrhagic (EHEC) strain designated E. coli O157:H7. E. coli is a normal inhabitant of the intestines of all animals, including humans. When aerobic culture methods are used, E. coli is the dominant species found in feces. Normally E. coli serves a useful function in the body by suppressing the growth of harmful bacterial species and by synthesizing appreciable amounts of vitamins. A minority of E. coli strains are capable of causing human illness by several different mechanisms. E. coli serotype O157:H7 is a rare variety of E. coli that produces large quantities of one or more related, potent toxins that cause severe damage to the lining of the intestine. These toxins [verotoxin (VT), shiga-like toxin] are closely related or identical to the toxin produced by Shigella dysenteriae.

 E. coli 0157:H7 in drinking water -- US EPA

However, some have been waterborne.  In 1999, people became sick after drinking contaminated water in Washington County, New York and swimming in contaminated water in Clark County, Washington.  Information about the health effects of E. coli O157:H7, and actions you can take to protect yourself and your family from E. coli infection is provided below.  

What are fecal coliforms?

Fecal coliforms are bacteria that are associated with human or animal wastes.  They usually live in human or animal intestinal tracts, and their presence in drinking water is a strong indication of recent sewage or animal waste contamination. 

How does E. coli or other fecal coliforms get in the water?

E. coli comes from human and animal wastes.  During rainfalls, snow melts, or other types of precipitation, E. coli may be washed into creeks, rivers, streams, lakes, or groundwater.  When these waters are used as sources of drinking water and the water is not treated or inadequately treated, E. coli may end up in drinking water. 

What are the health effects of E. coli O157:H7?

E. coli O157:H7 is one of hundreds of strains of the bacterium E. coli.  Although most strains are harmless and live in the intestines of healthy humans and animals, this strain produces a powerful toxin and can cause severe illness.  Infection often causes severe bloody diarrhea and abdominal cramps; sometimes the infection causes non-bloody diarrhea.  Frequently, no fever is present.  It should be noted that these symptoms are common to a variety of diseases, and may be caused by sources other than contaminated drinking water. 

In some people, particularly children under 5 years of age and the elderly, the infection can also cause a complication called hemolytic uremic syndrome, in which the red blood cells are destroyed and the kidneys fail. About 2%-7% of infections lead to this complication. In the United States, hemolytic uremic syndrome is the principal cause of acute kidney failure in children, and most cases of hemolytic uremic syndrome are caused by E. coli O157:H7. Hemolytic uremic syndrome is a life-threatening condition usually treated in an intensive care unit. Blood transfusions and kidney dialysis are often required. With intensive care, the death rate for hemolytic uremic syndrome is 3%-5%.

How long does it take for these symptoms of E. coli O157:H7 infection to occur?

Symptoms usually appear within 2 to 4 days, but can take up to 8 days.  Most people recover without antibiotics or other specific treatment in 5-10 days. There is no evidence that antibiotics improve the course of disease, and it is thought that treatment with some antibiotics may precipitate kidney complications. Antidiarrheal agents, such as loperamide (Imodium), should also be avoided. 

What should I do if I have any of the above symptoms?

Consult with your physician.  Infection with E. coli O157:H7 is diagnosed by detecting the bacterium in the stool. Most laboratories that culture stool do not test for E. coli O157:H7, so it is important to request that the stool specimen be tested on sorbitol-MacConkey (SMAC) agar for this organism. All persons who suddenly have diarrhea with blood should get their stool tested for E. coli O157:H7. 

Are there groups of people who are at greater risk of getting any of the symptoms?

Children under the age of five, the elderly, and people whose health is weakened (i.e., people who have long-term illnesses such as cancer or AIDS) are at greater risk of severe illness.

What should these people who are at greater risk do?  Are there any additional precautions they should take?

People who are at greater risk should consult with their doctor or health care provider and follow the instructions provided. 

How will I know if my water is safe?

If you get your water from a public water system, then your water system is required by law to notify you if your water is not safe.  If you are interested in obtaining information about your drinking water, consult the water quality report that you should receive annually from your local water system, or call your local water system directly.  

How is water treated to protect me from E. coli?

The water can be treated using chlorine, ultra-violet light, or ozone, all of which act to kill or inactivate E. coli.  Systems using surface water sources are required to disinfect to ensure that all bacterial contamination is inactivated, such as E. coli.  Systems using ground water sources are not required to disinfect, although many of them do.

If I have a private well, how can I have it tested for E. coli?

If you have a private well, you should have your water tested periodically.  Contact your State laboratory certification officer to find out which laboratories have been certified for conducting total coliform analyses.  (You may contact the Safe Drinking Water Hotline at 1-800-426-4791 for the address and phone number of this individual.)  Then contact a certified lab near you and get instructions on how to send them a water sample.  Typically, the lab will first test for total coliforms, which is a group of related organisms that is common in both the environment and in the gut of animals.  If the sample is positive for total coliforms, the lab will determine whether E. coli is also present.  E. coli is a type of total coliform that is closely associated with recent fecal contamination.  Few E. coli strains cause disease.  However, the presence of any E. coli in a water sample suggests that disease-causing organisms, are also likely to be present.

One of the strains of E. coli that causes disease is E. coli O157:H7.  EPA does not believe it necessary for an owner of a private well to test specifically for this organism under normal circumstances.  If E. coli O157:H7 is present in your well, it is highly likely that other strains of E. coli are also present.  If a well is E. coli-positive, regardless of strain, you should not drink the water unless it is disinfected.  Several tests are available for determining whether E. coli O157:H7 is present, but they are somewhat more expensive than the standard E. coli tests and many labs may not have the expertise or supplies to perform these tests.  Your state's laboratory certification officer should be able to tell you which laboratories can perform these tests, or you can contact the lab directly.

If my well is contaminated with E. coli, what can I do to protect myself?

If your well tests positive for E. coli, do not drink the water unless you boil it for at least one minute at a rolling boil, longer if you live at high altitudes.  You may also disinfect the well according to procedures recommended by your local health department.  Monitor your water periodically after disinfection to make certain that the problem does not recur.  If the contamination is a recurring problem, you should investigate the feasibility of drilling a new well or install a point-of-entry disinfection unit, which can use chlorine, ultraviolet light, or ozone.

How does the U.S. Environmental Protection Agency regulate E. coli?

According to EPA regulations, a system that operates at least 60 days per year, and serves 25 people or more or has 15 or more service connections, is regulated as a public water system under the Safe Drinking Water Act.  If a system is not a public water system as defined by EPA's regulations, it is not regulated under the Safe Drinking Water Act, although it may be regulated by state or local authorities. 

Under the Safe Drinking Water Act, EPA requires public water systems to monitor for coliform bacteria.  Systems analyze first for total coliform, because this test is faster to produce results.  Any time that a sample is positive for total coliform, the same sample must be analyzed for either fecal coliform or E. coli.  Both are indicators of contamination with animal waste or human sewage. 

The largest public water systems (serving millions of people) must take at least 480 samples per month.  Smaller systems must take at least five samples a month unless the state has conducted a sanitary survey – a survey in which a state inspector examines system components and ensures they will protect public health – at the system within the last five years.

Systems serving 25 to 1,000 people typically take one sample per month.  Some states reduce this frequency to quarterly for ground water systems if a recent sanitary survey shows that the system is free of sanitary defects.  Some types of systems can qualify for annual monitoring.

Systems using surface water, rather than ground water, are required to take extra steps to protect against bacterial contamination because surface water sources are more vulnerable to such contamination.  At a minimum, all systems using surface waters must disinfect.  Disinfection will kill E. coli O157:H7.

What can I do to protect myself from E. coli O157:H7 in drinking water?

Approximately 89 percent of Americans are receiving water from community water systems that meet all health-based standards.  Your public water system is required to notify you if, for any reason, your drinking water is not safe.  If you wish to take extra precautions, you can boil your water for one minute at a rolling boil, longer at higher altitudes.  To find out more information about your water, see the Consumer Confidence Report from your local water supplier or contact your local water supplier directly.  

If you draw water from a private well, you can contact your state health department to obtain information on how to have your well tested for total coliforms and E. coli contamination.  If your well tests positive for E. coli, there are several steps that you should take: (1) begin boiling all water intended for consumption, (2) disinfect the well according to procedures recommended by your local health department, and (3) monitor your water quality to make certain that the problem does not recur.  If the contamination is a recurring problem, you should investigate the feasibility of drilling a new well or install a point-of-entry disinfection unit, which can use chlorine, ultraviolet light, or ozone.

The Centers for Disease Control and Prevention (CDC) suggests other actions that you may take to prevent E. coli infection.  These include:

• Avoid swallowing lake or pool water while swimming.
  
• Thoroughly cook ground beef and avoid unpasteurized milk. 
  
• Make sure that persons with diarrhea, especially children, wash their hands carefully with soap after bowel movements to reduce the risk of spreading infection, and that persons wash hands after changing soiled diapers. Anyone with a diarrheal illness should avoid swimming in public pools or lakes, sharing baths with others, and preparing food for others. 
  
• Cook all ground beef and hamburger thoroughly. Because ground beef can turn brown before disease-causing bacteria are killed, use a digital instant-read meat thermometer to ensure thorough cooking. Ground beef should be cooked until a thermometer inserted into several parts of the patty, including the thickest part, reads at least 160º F. Persons who cook ground beef without using a thermometer can decrease their risk of illness by not eating ground beef patties that are still pink in the middle. 
  
• If you are served an undercooked hamburger or other ground beef product in a restaurant, send it back for further cooking. You may want to ask for a new bun and a clean plate, too. 
  
• Avoid spreading harmful bacteria in your kitchen. Keep raw meat separate from ready-to-eat foods. Wash hands, counters, and utensils with hot soapy water after they touch raw meat. Never place cooked hamburgers or ground beef on the unwashed plate that held raw patties. Wash meat thermometers in between tests of patties that require further cooking. 
  
• Drink only pasteurized milk, juice, or cider. Commercial juice with an extended shelf-life that is sold at room temperature (e.g. juice in cardboard boxes, vacuum sealed juice in glass containers) has been pasteurized, although this is generally not indicated on the label. Juice concentrates are also heated sufficiently to kill pathogens. 
  
• Wash fruits and vegetables thoroughly, especially those that will not be cooked. Children under 5 years of age, immunocompromised persons, and the elderly should avoid eating alfalfa sprouts until their safety can be assured. Methods to decontaminate alfalfa seeds and sprouts are being investigated. 

Will a water filter work to keep E. coli out of my water?

Most in-home filters will not.  EPA recommends that you boil your water if you are concerned about its safety. Distillation is the ONLY process that BOILS the water. Health departments around the world agree that boiling the water is the most fundamental way to kill biological contaminants. In distillation you only take the pure steam that comes off the water, thus leaving the dead bacteria and other contaminants behind.
 

Enterotoxigenic Escherichia coli (ETEC)

Frequently Asked Questions

• What is ETEC?
• What illess does ETEC cause?
• How does someone become infected with ETEC?
• How is infection with ETEC diagnosed?
• How is infection with ETEC treated?
• What are the long-term consequences of infection?
• What can be done to prevent infection with ETEC?
• Are antibiotics recommended to prevent ETEC?
• What is CDC doing to prevent ETEC?
• What can you do to prevent ETEC infection?

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Enterotoxigenic E. coli, a common cause of bacterial diarrhea

Enterotoxigenic Escherichia coli, or ETEC, is an important cause of bacterial diarrheal illness. Infection with ETEC is the leading cause of travelers' diarrhea and a major cause of diarrheal disease in underdeveloped nations, especially among children. ETEC is transmitted by food or water contaminated with animal or human feces. Although ETEC causes a significant amount of illness worldwide, the infection will end on its own and is rarely life-threatening.

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What is ETEC?

Escherichia coli is a bacterium that normally lives in the intestines of humans and other animals. Most types of E. coli are harmless, but some can cause disease. Disease-causing E. coli are grouped according to the different ways by which they cause illness. Enterotoxigenic Escherichia coli, or ETEC, is the name given to a group of E. coli that produce special toxins which stimulate the lining of the intestines causing them to secrete excessive fluid, thus producing diarrhea. The toxins and the diseases that ETEC causes are not related to E. coli O157:H7.

ETEC was first recognized as a cause of human diarrheal illness in the 1960s. It have since emerged as a major bacterial cause of diarrhea among travelers and children in the developing world. ETEC is increasingly recognized as an important cause of foodborne illness in developed nations, such as the United States.

ETEC produces two toxins, a heat-stable toxin (known as ST) and a heat-labile toxin (LT). Although different strains of ETEC can secrete either one or both of these toxins, the illness caused by each toxin is similar.

What illness does ETEC cause?

Infection with ETEC can cause profuse watery diarrhea and abdominal cramping. Fever, nausea with or without vomiting, chills, loss of appetite, headache, muscle aches and bloating can also occur but are less common. Illness develops 1-3 days after exposure and usually lasts 3-4 days. Some infections may take a week or longer to resolve. Symptoms rarely last more than 3 weeks. Most patients recover with supportive measures alone and do not require hospitalization or antibiotics.

How does someone become infected with ETEC?

Infection occurs when a person eats food, or drinks water or ice contaminated with ETEC bacteria. Human or animal wastes (e.g., feces) are the ultimate source of ETEC contamination.

How is infection with ETEC diagnosed?

In the laboratory, infection with ETEC is diagnosed when the bacteria are cultured from samples of stool. The techniques necessary to identify ETEC are not widely available, and physicians may make the diagnosis based on a patient's history and symptoms. If ETEC is suspected, the microbiology laboratory evaluating a patient's stool specimen should be alerted.

How is infection with ETEC treated?

Most infected persons will recover within a few days, without requiring any specific treatment.

Clear liquids are recommended for persons with diarrhea to prevent dehydration and loss of electrolytes. For adults, packaged oral rehydration salts or premixed oral rehydration solutions (both available over-the-counter) may be used, although traditional remedies with salty liquids such as chicken soup are also effective. Bismuth subsalicylate compounds (e.g., Pepto-Bismol) can help reduce the number of bowel movements. Although antimotility agents (e.g., Imodium, Lomotil) can effectively relieve ETEC-associated diarrhea and cramps, they may prolong the time it takes the body to rid itself of the toxin. Antimotility medications should be avoided by persons with high fevers or bloody diarrhea, and should be discontinued if diarrhea symptoms persist more than 48 hours. There are no data showing that kaolin-pectin compounds (e.g., Kaopectate) or lactobacillus slows diarrhea or relieves abdominal cramping.

Antibiotics can shorten the duration of diarrheal illness and discomfort, especially if given early, but they are usually not required. ETEC is frequently resistant to common antibiotics, including trimethoprim-sulfamethoxazole and ampicillin. Because resistance to antibiotics is increasing worldwide, the decision to use an antibiotic should be carefully weighed against the severity of illness and the risk of adverse reactions, such as rash, antibiotic-associated colitis, and vaginal yeast infection. Fluoroquinolones have been shown to be effective therapy.

What are the long-term consequences of infection?

Virtually all persons recover completely without any long-term consequences.

What can be done to prevent infection with ETEC?

For travelers in developing countries, ETEC infection can be prevented by avoiding foods and beverages that could be contaminated with bacteria. Although both cooked and uncooked foods have been associated with ETEC infections, high-risk foods are raw fruits and vegetables (e.g., salads), raw seafood or undercooked meat or poultry, unpasteurized dairy products, food from street vendors, and untreated water (including ice) in areas lacking adequate chlorination.

There have been rare cases of ETEC infection reported in the United States associated with eating salads, raw fruits, and vegetables. However, these foods are generally safe if handled and prepared appropriately.

In developing countries, food can be made safe to eat by thoroughly cooking it and by keeping it hot. Fruits and vegetables should be peeled by the person eating them. Water used for drinking (including brushing teeth) or for washing food in these countries should be bottled, boiled, or chemically treated with iodine, chlorine or another disinfectant. Handwashing with soap and water also can prevent contamination of food and beverages with ETEC and prevent transmission from person to person as well. Bismuth subsalicylate preparations (1 oz of liquid or two 262.5-mg tablets taken four times daily) can reduce the risk of becoming infected with ETEC and other common bacteria that cause diarrhea. Persons with kidney disease should consult a physician before taking medications with large amounts of salicylate.

Vaccines for ETEC are being developed, but none are currently available.

Are antibiotics recommended to prevent ETEC?

Taking antibiotics to prevent ETEC infection is generally not recommended. Pregnant women and persons with weakened immune systems (such as patients who are receiving chemotherapy, who are taking immunosuppressive medications, or who have HIV infection) should talk with their health care provider if they are traveling to areas at high risk for ETEC exposure.

What is CDC doing to prevent ETEC?

CDC provides advice to travelers and travel medicine clinics about ETEC infection, and assists health care providers as well as state and county health departments with ETEC diagnosis and investigations of ETEC outbreaks. In addition, CDC, in collaboration with international agencies, works to improve sanitary conditions in foreign accommodations (e.g., tourist resorts) and on board cruise ships docking in U.S. ports. Finally, CDC is working to improve methods for diagnosing ETEC.

What can you do to prevent ETEC infection?

If you are traveling to developing countries where the risk of travelers' diarrhea is increased:

• Eat thoroughly cooked foods prepared in facilities that practice proper food handling techniques.
• Consume pasteurized milk and milk products.
• Drink bottled beverages, beverages with water that has been boiled 5 minutes or longer, or municipal water that has been adequately treated with chlorine or other appropriate chemical disinfectant.
• Avoid: .
  • Raw foods (e.g., salads, peeled fruit or vegetables, raw seafood, undercooked meat or poultry)
  • Food from street vendors
  • Unpasteurized dairy products
  • Drinking water (including ice in beverages) from sources where there is any question as to the quality of the water supply

To reduce the risk of spreading the infection, make sure that infected persons, especially children, wash their hands carefully and frequently with soap and do not prepare or handle foods.