Which Waterborne Contaminants Cause Diarrhea?
A wide variety of waterborne viruses, bacteria, and parasites
can cause acute diarrhea. These include Cryptosporidia,
Salmonella , Shigella, Campylobacter jejuni, rotavirus, E. coli
O157:H7 and other pathogenic E. coli species, Giardia, and
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
caliciviruses ( 1,2). The reported cases of waterborne disease
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
Disease Control and Prevention ( 2). Typical stool sampling
does not include many common pathogens, such as
Cryptosporidium , and viral agents are often difficult to detect
in clinical samples ( 2). See PSR’s fact sheets on Cryptosporidium
and E. coli for more information.
Who is Most Susceptible to Diarrhea Caused by Contaminants in Drinking Water?
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
that are insensitive to disinfection, like Cryptosporidia, enter
the water supply . Certain populations are at greater risk of
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.
Children
In the years between 1979 and 1992, diarrhea contributed
to 12% of U.S. hospitalizations of children one month
through four years of age ( 3). Infectious diarrhea is
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
( 4). The immature immune systems of young children,
combined with the wearing of diapers, crowded conditions
in some day care situations, and typical hand-to-mouth
be
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