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INTRODUCTION: Cryptosporidium
is a parasite commonly found in lakes and rivers, especially when the water is
contaminated with sewage and animal wastes. Cryptosporidium is very resistant
to disinfection, and even a well-operated water treatment system cannot ensure
that drinking water will be completely free of this parasite. Current EPA drinking
water standards were not explicitly designed to assure the removal or killing
of Cryptosporidium. Many large water systems already voluntarily take
actions for greater control of Cryptosporidium and other microbial contaminants.
By 2001, the water systems serving the majority of the United States population
(those relying on a surface water source, such as a river, and serving more than
10,000 people) must meet a new EPA standard that strengthens control over microbial
contaminants, including Cryptosporidium. EPA continues to conduct research
on microbial contaminants which will be used for determining priorities for the
drinking water program, including setting future standards and reevaluating existing
standards. Cryptosporidium
has caused several large waterborne disease outbreaks of gastrointestinal illness,
with symptoms that include diarrhea, nausea, and/or stomach cramps. People with
severely weakened immune systems (that is, severely immunocompromised) are likely
to have more severe and more persistent symptoms than healthy individuals. Moreover,
Cryptosporidium has been a contributing cause of death in some immunocompromised
people. Individuals who are severely immunocompromised may include those who are
infected with HIV/AIDS, cancer and transplant patients taking immunosuppressive
drugs, and people born with a weakened immune system. BACKGROUND: Data
are not adequate to determine how most people become infected. For example, we
do not know the importance of drinking water compared to other possible sources
of Cryptosporidium, such as exposure to the feces of infected persons
or animals, sex involving contact with feces, eating contaminated food, or accidentally
swallowing contaminated recreational water. Thus,
in the absence of an outbreak, there are insufficient data to determine whether
a severely immunocompromised individual is at a noticeably greater risk than the
general public from waterborne Cryptosporidiosis. Even a low level of
Cryptosporidium in water, however, may be of concern for the severely
immunocompromised, because the illness can be life-threatening. The risk of a
severely immunocompromised individual acquiring Cryptosporidiosis from
drinking water in the absence of an outbreak is likely to vary from city to city,
depending on the quality of the city's water source and the quality of water treatment.
Current risk data are not adequate to support a recommendation that severely immunocompromised
persons in all U.S. cities boil or avoid drinking tap water. In
the absence of a recognized outbreak, this guidance has been developed for severely
immunocompromised people who may wish to take extra precautions to minimize their
risk of infection from waterborne Cryptosporidiosis. To be effective,
the guidance must be followed consistently for all water used for drinking
or for mixing beverages. During outbreaks of waterborne Cryptosporidiosis,
studies have found that people who used precautions only part of the time were
just as likely to become ill as people who did not use them at all.
GUIDANCE:EPA
and CDC have developed the following guidance for severely immunocompromised people
who may wish to take extra precautions. Such individuals should consult with their
health care provider about what measures would be most appropriate and effective
for reducing their overall risk of Cryptosporidium and other types of
infection. Although
data are not sufficient for EPA/CDC to recommend that all severely immunocompromised
persons take extra caution with regards to their drinking water, individuals who
wish to take extra measures to avoid waterborne Cryptosporidiosis can
bring their drinking water to a full boil for one minute. Boiling water
is the most effective way of killing Cryptosporidium. As
an alternative to boiling water, people may use the following measures: *
A point-of-use (personal use, end-of-tap, under-sink) filter. Only point-of-use
filters that remove particles one micrometer or less in diameter should be considered.
Filters in this category that provide the greatest assurance of Cryptosporidium
removal include those that use reverse osmosis, those labeled as "Absolute" one
micrometer filters, or those labeled as certified by NSF International (National
Sanitation Foundation) under standard 53 for "Cyst Removal." The "Nominal" one
micrometer rating is not standardized and many filters in this category may not
reliably remove Cryptosporidium. As with all filters, people should follow
the manufacturer's instructions for filter use and replacement. Water treated
with a point-of-use filter that meets the above criteria may not necessarily be
free of organisms smaller than Cryptosporidium that could pose a health
hazard for severely immunocompromised individuals. | FURTHER
INFORMATION: When
an outbreak of waterborne Cryptosporidiosis is recognized and is determined
to be on-going, officials of the public-health department and/or the water utility
will normally issue a "boil water" notice to protect both the general public and
the immunocompromised. Current
testing methods cannot determine with certainty whether Cryptosporidium
detected in drinking water is alive or whether it can infect humans. In addition,
the current method often requires several days to get results, by which time the
tested water has already been used by the public and is no longer in the community's
water pipes. Severely
immunocompromised people may face a variety of health risks. Depending on their
illness and circumstances, a response by such individuals that focuses too specifically
on one health risk may decrease the amount of attention that should be given to
other risks. Health care providers can assist severely immunocompromised persons
in weighing these risks and in applying this guidance. As
part of the Drinking Water and Health pages, this fact sheet is part of a larger
U.S. EPA publication:
EPA National Primary Drinking Water Regulations |
