E. COLI: Questions & Answers

Monica Farley, M.D.
Associate Professor of Medicine, Division of Infectious Diseases
Emory University School of Medicine
Atlanta Veterans Affairs Medical Center
404-728-7688


Dr. Farley is principal investigator for the Georgia branch of the Emerging Infections Program (EIP), a national network consisting of the Centers for Disease Control and Prevention (CDC) and state health departments in collaboration with academic institutions, local health departments, and organizations of health professionals. As part of the EIP activities, Emory, the Atlanta Veterans Affairs Medical Center, and the Georgia Department of Human Resources collect information for FoodNet (Foodborne Diseases Active Surveillance Network). FoodNet is a surveillance system that tries to identify all cases of foodborne disease (including E. coli) in the 20-country metro area, identify risks for acquiring infections, and document the disease burden in the community. FoodNet is in contact twice a week with all labs that process stool cultures. It is a collaborative project of the , U.S. Department of Agriculture, U.S. Food and Drug Administration and seven health department-based programs around the country

Q. How was the connection made between the beef served in Madison County schools and the Escherichia coli 0157 outbreak at White Water park?

A. The DNA fingerprint of the E. coli 0157 in the Madison County beef and all of the White Water E. coli isolates available for fingerprinting were identical. The fingerprint pattern is otherwise unusual in this area. That gives us a very strong clue that there may be a relationship. However, there has not really been an epidemiologic connection yet. That kind of connection would have to be established by what is called "shoe leather" epidemiology, in which researchers go from person to person trying to link the cases by identifying all contacts, questioning about food intake, common exposures, common neighborhoods, common swimming pools, day cares, etc. That is a tedious, detailed way to determine how the bacteria spread from person to person.

Q. Is it unusual for E. coli to move from an origin in beef into water?

A. Most often, E. coli has been a contamination problem in food, with the source most often being cattle. Ingestion of undercooked hamburger is the most common way people are exposed to this bacteria. Things that occur in the growing process itself though, within the farm setting, also can cause contamination. For example, produce can be contaminated with cattle feces, or fertilizer can contaminate produce. Also, if produce, such as apples or lettuce is not cooked, pasteurized or adequately washed it can be a source of contamination. Once a person is infected, diarrhea is part of the clinical disease process. The disease can then be spread from person to person through fecal-oral contamination. This is more likely to happen in a setting like a day care, but it could happen anywhere. As we know, E. coli can get into the water and contaminate it, either through sewage or through fecal accidents in lakes or municipal pools.

Q. How likely is it that an exposure will occur while swimming?

A. First of all, in order for an infection with E. coli to occur in a pool or lake, a person must swallow some contaminated water. You don't get an infection through your skin, for example, by just standing in the water. This may explain why few older children and no adults were infected in the White Water cases. Also, there must be sufficient bacteria present to remain infectious despite dilution in the water, combined with a low level of chlorine at that particular time. The proper level of chlorination but time could elapse between bacteria going into the water and the chlorine killing the bacteria. The White Water incident was clearly an unusual occurrence.

Q. What about swimming in lakes?

A. Although E. coli is more likely to be diluted in a lake setting, it also can survive for much longer because of the lack of chlorination. You are more likely to be exposed in a concentrated swimming area at a lake, like a beach. more

Q. Does E. coli make some people sicker than others?

A. There is always a percentage of people in an outbreak who do not get as sick. From all the outbreaks that have been tracked, 23 percent of affected persons have been hospitalized and six percent have developed hemolytic uremic syndrome. One percent have died. Clearly there is a mild and probably asymptomatic form. Many times people have non-bloody diarrhea and are not very ill. Children seem to get sicker overall.

Q. If one member of a family has an infection from E. coli, how likely is it that another member will get it?

A. There are several ways family members might become infected. There might be a common food source, for example. Or there could be secondary cases within a family through fecal-oral spread. These occur more frequently in the very young and the very old. If you initiate very careful hand washing and take reasonable precautions you can often avoid these exposures.

Q. Are we likely to have more outbreaks of E. Coli?. Is this an increasing problem?

A. Part of our job with EIP and FoodNet is to monitor cases. E. coli was not even recognized as a problem until 1982. In Atlanta, we have been monitoring E. coli cases for about three years. We monitor sporadic cases as well as larger outbreaks and connect them to food products and other exposures. Clearly the White Water outbreak represented a big increase in the number of cases. Current methods of food processing and food distribution patterns and the increasing habit of using preprocessed foods have the potential of causing an increase in infections.

Q. Are there many different strains of E. coli?

A. E. coli is one of a large group of organisms with different variants. E. coli 0157 is a particular serologic variant.

Q. Is there any treatment for an E. coli infection?

A. This particular E. coli type (0157) produces toxins, which are responsible for most of the serious complications. There is no evidence that antibiotics are beneficial in treating E. coli, and some think they may even be harmful. Experimental treatments are being investigated, including an anti-toxin product that binds the toxin in the gastrointestinal tract. Early results show that these might be beneficial. Otherwise, treatment includes support for complications including bleeding disorders and kidney failure. Sometimes dialysis and ventilation are necessary.

Q. How should people avoid being exposed to E. coli in water?

A. There are several common sense ways to avoid exposure. The risk of exposure is low, because the bacteria should be killed by chlorine. But the risk does depend on the level of contamination, the chlorine level, and the amount of time the chlorine has to kill the E. coli. Do not take sick children, particularly young ones, to swim in a public pool. Older children who do not need to be in baby pools should avoid them. Avoid swallowing water in a pool or lake.