AIDS Treatment News Issue #227, July 21, 1995
Cryptosporidiosis is caused by a microscopic parasite,
Cryptosporidium parvum, and may cause severe diarrhea.
Persons with normal immunity get cryptosporidiosis, but
recover without treatment within several weeks. In persons
with immune deficiency, however, the disease can be life-
threatening; there are treatments which sometimes reduce the
symptoms, but no known treatment is effective in getting rid
of the parasite in severely immunosuppressed persons.
Cryptosporidium is spread by contaminated water, as well as
by contact with infected persons or animals. The risk from
water came to national attention in 1993, when over 400,000
people got cryptosporidiosis from the Milwaukee water supply,
despite purification according to Federal standards.
Cryptosporidium can be found in most U.S. rivers, lakes, and
streams. While a well-operated and equipped municipal water
purification system can remove most of it in drinking water,
these systems cannot guarantee its complete removal.
On June 16, 1995, the U.S. Centers for Disease Control and
Prevention (CDC) issued guidance regarding Cryptosporidium
and water supplies.(1) This 19-page document includes two and
a half pages concerning immunocompromised persons. Points
* "All immunocompromised persons should be educated and
counseled about the ways that Cryptosporidium can be
transmitted (e.g., sexual practices involving fecal
exposure, contact with infected adults or with infected
children who wear diapers, contact with infected animals,
drinking or eating contaminated water or food, and exposure
to contaminated recreational water."
* "All persons, especially immunocompromised persons, should
avoid drinking water directly from lakes or rivers. Because
water can be ingested unintentionally, immunocompromised
persons should be advised that swimming in lakes, rivers,
or public swimming pools can also place them at increased
risk for infection."
* "During waterborne outbreaks or other situations in which a
community boil-water advisory is issued, immunocompromised
persons should boil water for 1 minute to eliminate the
risk for acquiring cryptosporidiosis. Using submicron,
personal- use filters (i.e., home or office types of water
filters) or high-quality bottled water also can reduce the
risk for transmission. However, boiling water is the most
certain method of killing Cryptosporidium oocysts [the
infectious stage of the parasite's life cycle]."
* "Only microstraining filters capable of removing particles
less than or equal to 1 micrometer in size should be used
by immunocompromised persons and other persons who choose
to use a personal-use filter (i.e., home or office water
filters) to reduce the risk for transmission of
Filters in this category that provide the greatest
certainty of Cryptosporidium removal include those that
produce water by reverse osmosis, those labeled according
to filter manufacturing industry standards as "Absolute" 1
micrometer filters, and those labeled as meeting American
National Standards Institute (ANSI)/NSF (formerly the
National Sanitary Foundation) International Standard #53
for "Cyst Removal." [Footnote: NSF International certifies
water filters according to the ANSI/NSF International
Standard #53: Drinking Water Treatment Units -- Health
To obtain information regarding the current status of any
water filter, contact NSF International, 3475 Plymouth
Road, P.O. Box 130140, Ann Arbor, Michigan 48113-0140.
Telephone 800/673- 8010.] The "Nominal" 1 micrometer filter
rating is not standardized, and many filters in this
category might not reliably remove oocysts.
Filters that only employ ultraviolet light, activated
carbon, or pentiodide-impregnated resins are not effective
against Cryptosporidium. Not all filters advertised as
effective against Giardia are effective against
Because bacterial overgrowth on filters can be a additional
health risk and oocysts are likely to concentrate on the
outside of filter cartridges, persons should carefully
follow the manufacturer's instructions for filter
replacement and use.
Immunocompromised patients should either have someone else
change the used cartridges or use disposable gloves if they
themselves change the cartridges."
* In a longer discussion on bottled water, the CDC
recommendations noted, "Many brands of bottled water
adequately reduce the risk for cryptosporidiosis and, thus,
provide a reasonable alternative to boiling tap water.
However, labeling of bottled water is not standardized with
regard to the manufacturing practices used to test for and
remove or kill Cryptosporidium oocysts...." The
recommendation discusses risks from different sources of
bottled water. But whatever the source, "Bottlers who treat
water before bottling by distillation or reverse osmosis
filtration, regardless of the source (e.g. well, spring,
and municipal tap water), insure removal of oocysts if they
are present. Similarly, water that has been passaged
through an "Absolute" 1 micrometer or smaller filter or
through a filter labeled as meeting ANSI/NSF International
Standard #53 for "Cyst Removal" before bottling will
provide almost the same level of oocyst removal..." The
document suggests, "Persons who use bottled water as an
alternative to tap water that has been boiled must
carefully research and choose their supplier."
Unfortunately no list of safe waters is provided; there is
a voluntary effort by the bottling industry to improve
labeling, but it will probably take about a year to put
"Current data are inadequate to make a general recommendation
that immunocompromised persons in the United States boil or
avoid drinking tap water in nonoutbreak settings. However,
immunocompromised persons should be advised that the risk for
waterborne transmission is possible and that they can choose
to reduce their risk for waterborne cryptosporidiosis by
using precautions similar to those recommended during
outbreaks. Immunocompromised persons should consult their
health-care provider before making such a decision."
Whatever precaution one uses, it is important to use them for
all water consumed. "Preliminary data from outbreak
investigations indicate that persons who did not consistently
use bottled water or filters were as likely to become ill as
those who did not use such products."
Who Is at Risk?
We asked Dr. Dennis D. Juranek at the CDC who should be most
concerned about water safety -- is there any agreement that
people below a certain CD4 (T-helper) count should take the
special precautions? He said that had been discussed in the
workshop which developed the guidelines. But while clearly
those with low CD4 counts -- under 200, or especially under
100 -- are at greater risk for getting serious illness
immediately from Cryptosporidium, it may be possible that
persons earlier in HIV disease could recover from
cryptosporidiosis but not clear the parasite completely,
allowing it to cause serious illness later. Until more is
known about this possibility, the guidelines are targeted at
everyone with HIV.
Dr. Juranek explained that the CDC did not have enough
information to issue a "recommendation" that
immunocompromised persons not use tap water everywhere in the
U.S., and issued "guidance" instead. "Basically the reason is
that we do not know what the magnitude of risk is for
acquiring Cryptosporidium from drinking water during non-
outbreak periods, and we do not know what percent of
Cryptosporidium infections are acquired from drinking water
vs. the other modes of transmission. We have some preliminary
data indicating that sexual practices that result in fecal
exposure may be among the highest risk activities; remember
that not all Cryptosporidium infections in HIV/AIDS patients
"Also, the risk of waterborne infection is likely to vary
considerably from city to city depending on the quality of a
city's source of drinking water and water treatment
processes. For example, in some cities water comes from high-
quality well water (no evidence of fecal contamination ever).
Persons in such towns would not be at risk for waterborne
cryptosporidiosis. Other towns have a lot of human sewage
discharge upstream (sewage treatment does not kill all
Cryptosporidium), and even brief treatment interruptions at a
water treatment plant using such water may place AIDS
patients at high risk.
"We are also concerned about the life-style changes that may
be necessary for a person to make sure that all his/her
drinking water is boiled/filtered/bottled. This basically
means that one has to carry water to work and for recreation,
e.g. no fountain drinks (syrup mixed with carbonated tap
water) at fast food establishments, restaurants, movie
theaters, etc. At home people would have to remember to use
boiled, etc., water to prepare juices or other cold beverages
normally reconstituted with tap water.
"So the question each person must ask him/herself is, 'Is
this worth it? Is the waterborne risk in my town great enough
for me to do this?' We would not answer these questions for
immunosuppressed persons who live a variety of life styles in
cities whose water quality is also highly variable."
Bottled Water Quality
We also asked Dr. Juranek about choice of bottled water. He
said that there is no adequate technology today for testing
either bottled or city water to see if it is safe. Water
treated by distillation or reverse osmosis should be OK --
but if the label says it is treated by ultraviolet light,
ozone, or microfiltration, that may not be enough to remove
or kill the parasite.
Also, the source of the water is important. Water from a well
which is tested twice a week for years and has shown no fecal
contamination ever is probably free of the parasite. Some of
the major bottlers in Europe and the U.S. take pride in their
wells; they own the land around the site and take care of it
to maintain their water quality.
AIDS TREATMENT NEWS spoke with Donald P. Kotler, M.D., a
leading AIDS gastroenterologist. He is not happy that the CDC
refuses to make a recommendation on drinking water and leaves
it to each patient to make his or her own decision.
Dr. Kotler recommends taking the special precautions with
drinking water if one's CD4 count is below 200. This is based
on a study which found that above 190, people usually
recovered from cryptosporidiosis spontaneously, while below
190 they seldom did. Dr. Kotler said there is little evidence
that Cryptosporidium not being completely cleared is a common
problem, although of course there are asymptomatic cases. And
if a person is exposed to the parasite in the course of their
usual lifestyle, they have probably been exposed to it