A wide variety of waterborne viruses, bacteria, and parasites

the caliciviruses (i.e., Norwalk and Norwalk-like viruses).

Much of the time, the etiology of waterborne disease

outbreaks in the U.S. is unknown. In most cases, it is thought

that the illness is viral in nature, most likely caused by

probably represent only a small fraction of the outbreaks

that actually occur in the U.S. every year. It is very difficult

to connect individual cases of gastroenteritis, and most

waterborne diseases are not tracked by the Centers for

does not include many common pathogens, such as

In the U.S. and other developed countries, drinking water

disinfection has dramatically reduced gastrointestinal infections

from such waterborne pathogens as cholera and typhoid.

However, waterborne disease still occurs, usually because of

a breach in the water treatment system or because pathogens

diarrheal disease from waterborne pathogens. These include

the elderly, infants and young children, and individuals with

severely weakened immune systems, such as AIDS patients,

patients undergoing certain types of chemotherapy, and those

who have recently received organ transplants.

In the years between 1979 and 1992, diarrhea contributed

to 12% of U.S. hospitalizations of children one month

uncommon in newborns, though it can be deadly in this

age group. Infants who are bottle-fed may be particularly at

risk of exposure to waterborne pathogens through the use

of tap water to reconstitute formula. The rate of diarrheal

illness increases in children just weaned from breastfeeding,

peaks around two to three years of age, and then diminishes

combined with the wearing of diapers, crowded conditions

in some day care situations, and typical hand-to-mouth

behaviors make small children prone to infection and

important transmitters of diarrheal disease.

Diarrhea has been increasingly recognized as a serious

problem for the elderly, resulting in increased hospitalizations

and disease from microbial exposure due to many factors,

such as reduced immunity, frailty from malnutrition, or

existing chronic illness. They are at the highest risk for death

of deaths in diarrhea-related hospitalizations were in people

the case fatality rates for certain waterborne pathogens, such

Opportunistic pathogens can cause serious disease and death

in those with compromised immune systems. Diarrhea is

often much worse and more difficult to treat in people with

immunocompromised persons. Of those who died in the

Milwaukee cryptosporidiosis outbreak of 1993, the majority

Adenovirus-related diarrhea is a problem in such patients—

diarrheal illnesses are more likely to lead to more serious

problems, such as bloodstream infections and meningitis,

in the immunocompromised.

Waterborne disease can be a problem when private wells become

contaminated, public water supply treatment is inadequate, or

contamination occurs in the distribution system. The U.S.

Environmental Protection Agency (EPA) requires public water

systems to monitor treated drinking water for the presence of

total coliform bacteria, an indicator of the potential presence

of more pathogenic organisms. However, EPA does not regulate

levels of any contaminants in private wells. It is the responsibility

of well owners to have their water tested.

EPA requires all public water systems to regularly test for the

presence of coliform bacteria as an indicator that drinking water

may be contaminated by microbial pathogens from human or

animal waste. Public water systems using surface water or

groundwater under the influence of surface water must also

through annual Consumer Confidence Reports, if microbial

agents (or other regulated contaminants) are present at levels

above the legal limit. Recently, EPA also required that small public

water systems take additional action, such as better filtration of

water from surface sources, to reduce contamination.

? In cases of persistent or recurrent diarrhea ask the patients

about the source of drinking water (private well or public

system). Where contamination is suspected, encourage

patients to test their tap water and talk to them about

temporary alternatives such as bottled water. EPA and

CDC have developed specific guidance for persons with

severely weakened immune systems, available at http://

www.epa.gov/safewater/crypto.html.

? Advise patients who consume water from private wells to have

their water tested regularly for coliform bacteria. Maintaining

well integrity and sloping the area around private wells (to

drain surface runoff away) can prevent well contamination.

? Oral rehydration therapy can be used in ill patients to

avert hospitalizations from diarrheal dehydration.

? Encourage your patients to read the Consumer Confidence

Reports sent to them by public water suppliers. Utilities

are required to notify customers if any regulated

? Health care providers can help prevent waterborne disease

by joining local efforts to protect drinking water sources.

? Physicians for Social Responsibility: (202) 667-4260,

www.psr.org, or www.envirohealthaction.org

? NSF International: (800) 673-6275 or http://www.nsf.com/

? Campaign for Safe and Affordable Drinking Water: http://

www.safe-drinking-water.org/.

? EPA’s Safe Drinking Water Hotline: (800) 426-4791

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