This is a fact sheet about a contaminant that may be found in some public or
private drinking water supplies. It may cause health problems if found in
amounts greater than the health standard set by the United States
Environmental Protection Agency (EPA).
Cryptosporidium is a parasite that enters lakes and rivers through sewage and animal waste.
It causes cryptosporidiosis, a mild gastrointestinal disease. However, the disease
can be severe or fatal for people with severely weakened immune systems. EPA and
CDC have prepared advice for those with severely compromised immune systems who
are concerned about Cryptosporidium.
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.
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, 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.
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
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
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.
What is cryptosporidiosis?
Cryptosporidiosis is a diarrheal disease caused by microscopic parasites of the
genus Cryptosporidium. Once an animal or person is infected, the parasite lives
in the intestine and passes in the stool. The parasite is protected by an outer
shell that allows it to survive outside the body for long periods of time and
makes it very resistant to chlorine- based disinfectants. Both the disease and
the parasite are commonly known as "crypto."
During the past two decades, crypto has become recognized as one of the most
common causes of waterborne disease within humans in the United States. The
parasite may be found in drinking water and recreational water in every region
of the United States and throughout the world.
How is cryptosporidiosis spread?
Cryptosporidium lives in the intestine of infected humans or animals. Millions
of crypto germs can be released in a bowel movement from an infected human or
animal. Consequently, Cryptosporidium is found in soil, food, water, or surfaces
that have been contaminated with infected human or animal feces. If a person
swallows the parasite they become infected. You cannot become infected through
contact with blood. The parasite can be spread by;
Accidentally putting something into your mouth or swallowing something that has come into contact with feces of a person or animal infected with Cryptosporidium.
Swallowing recreational water contaminated with Cryptosporidium (Recreational water includes water
in swimming pools, hot tubs, jacuzzis, fountains, lakes, rivers, springs, ponds, or streams that can
be contaminated with sewage or feces from humans or animals.) Note: Cryptosporidium can
survive for days in swimming pools with adequate chlorine levels.
Eating uncooked food contaminated with Cryptosporidium. Thoroughly wash with clean, safe water all
vegetables and fruits you plan to eat raw. See below for information on making water safe.
Accidentally swallowing Cryptosporidium picked up from surfaces (such as bathroom fixtures,
changing tables, diaper pails, or toys) contaminated with feces from an infected person.
What are the symptoms of cryptosporidiosis?
The most common symptom of cryptosporidiosis is watery diarrhea. Other symptoms include:
Stomach cramps or pain
Some people with crypto will have no symptoms at all. While the small intestine is the site most
commonly affected , Cryptosporidium infections could possibly affect other areas of the digestive
or the respiratory tract .
How long after infection do symptoms appear?
Symptoms of cryptosporidiosis generally begin 2 to 10 days (average 7 days) after becoming infected
with the parasite.
How long will symptoms last?
In persons with healthy immune systems, symptoms usually last about 1 to 2 weeks. The symptoms
may go in cycles in which you may seem to get better for a few days, then feel worse again before
the illness ends.
If I have been diagnosed with Cryptosporidium , should I worry about spreading the infection to others?
Yes, Cryptosporidium can be very contagious. Follow these guidelines to avoid spreading the disease to others:
Wash your hands with soap and water after using the toilet, changing diapers, and before eating or preparing food.
Do not swim in recreational water (pools, hot tubs, lakes or rivers, the ocean, etc.) if you have cryptosporidiosis
and for at least 2 weeks after diarrhea stops. You can pass Cryptosporidium in your stool and contaminate water
for several weeks after your symptoms have ended. This has resulted in outbreaks of cryptosporidiosis among recreational water users.
Note: Cryptosporidium can be spread in a chlorinated pool because it is resistant to chlorine and, therefore,
can live for days in chlorine-treated swimming pools.
Who is most at risk for cryptosporidiosis?
People who are most likely to become infected with Cryptosporidium include:
Children who attend day care centers, including diaper-aged children
Child care workers.
Parents of infected children.
Backpackers, hikers, and campers who drink unfiltered, untreated water.
Swimmers who swallow water while swimming in swimming pools, lakes, rivers, ponds, and streams.
People who drink from shallow, unprotected wells.
People who swallow water from contaminated sources.
Contaminated water includes water that has not been boiled or filtered. Several community-wide
outbreaks of cryptosporidiosis have been linked to drinking municipal water or recreational water contaminated with Cryptosporidium.
Who is most at risk for getting seriously ill with cryptosporidiosis?
Although Crypto can infect all people, some groups are more likely to develop more serious illness.
Young children and pregnant women may be more susceptible to the dehydration resulting from diarrhea
and should drink plenty of fluids while ill.
If you have a severely weakened immune system, you are at risk for more serious disease.
Your symptoms may be more severe and could lead to serious or life-threatening illness. Examples of
persons with weakened immune systems include those with HIV/AIDS; cancer and transplant patients who
are taking certain immunosuppressive drugs; and those with inherited diseases that affect the immune system.
What should I do if I think I may have cryptosporidiosis?
If you suspect that you have cryptosporidiosis, see your health care provider.
How is a cryptosporidiosis diagnosed?
Your health care provider will ask you to submit stool samples to see if you are
infected. Because testing for Crypto can be difficult, you may be asked to submit
several stool specimens over several days. Tests for Crypto are not routinely done
in most laboratories; therefore, your health care provider should specifically
request testing for the parasite.
What is the treatment for cryptosporidiosis?
A new drug, nitazoxanide, has been approved for treatment of diarrhea caused by
Cryptosporidium in people with healthy immune systems. Consult with your health
care provider for more information. Most people who have a healthy immune system
will recover without treatment. The symptoms of diarrhea can be treated. If you have
diarrhea, drink plenty of fluids to prevent dehydration. Rapid loss of fluids from
diarrhea may be especially life threatening to babies; therefore, parents should talk
to their health care provider about fluid replacement therapy options for infants.
Anti-diarrheal medicine may help slow down diarrhea, but talk to your health care
provider before taking it.
People who are in poor health or who have a weakened immune system are at higher
risk for more severe and more prolonged illness. The effectiveness of nitazoxanide
in immunosuppressed individuals is unclear. For persons with AIDS, anti-retroviral
therapy that improves immune status will also decrease or eliminate symptoms of Crypto.
However, even if symptoms disappear, cryptosporidiosis is usually not curable and the
symptoms may return if the immune status worsens. See your health care provider to
discuss anti-retroviral therapy used to improve your immune status.
How can I prevent cryptosporidiosis?
Practice good hygiene.
Wash hands thoroughly with soap and water.
Wash hands after using the toilet and before handling or eating food (especially for persons with diarrhea).
Wash hands after every diaper change, especially if you work with diaper-aged children, even if you are wearing gloves.
Protect others by not swimming if you are experiencing diarrhea (essential for children in diapers).
Avoid water that might be contaminated.
Do not swallow recreational water.
Do not drink untreated water from shallow wells, lakes, rivers, springs, ponds, and streams.
Do not drink untreated water during community-wide outbreaks of disease caused by contaminated drinking water.
Do not use untreated ice or drinking water when traveling in countries where the water supply might be unsafe.
In the United States , nationally distributed brands of bottled or canned carbonated soft drinks are safe to drink.
Commercially packaged non-carbonated soft drinks and fruit juices that do not require refrigeration until after
they are opened (those that are stored unrefrigerated on grocery shelves) also are safe.
If you are unable to avoid using or drinking water that might be contaminated, then you can make
the water safe to drink by doing one of the following:
Heat the water to a rolling boil for at least 1 minute.
Use a filter that has an absolute pore size of at least 1 micron or one that has been NSF rated for "cyst removal."
Do not rely on chemicals to disinfect water and kill Cryptosporidium. Because it has a thick outer shell,
this particular parasite is highly resistant to disinfectants such as chlorine and iodine.
Avoid food that might be contaminated.
Wash and/or peel all raw vegetables and fruits before eating.
Use safe, uncontaminated water to wash all food that is to be eaten raw.
Avoid eating uncooked foods when traveling in countries with minimal water treatment and sanitation systems.
Take extra care when traveling.
If you travel to developing nations, you may be at a greater risk for Cryptosporidium infection
because of poorer water treatment and food sanitation. Warnings about food, drinks, and swimming
are even more important when visiting developing countries. Avoid foods and drinks, in particular
raw fruits and vegetables, tap water, or ice made from tap water, unpasteurized milk or dairy products,
and items purchased from street vendors. These items may be contaminated with Cryptosporidium.
Steaming-hot foods, fruits you peel yourself, bottled and canned processed drinks, and hot coffee
or hot tea are probably safe. Talk with your health care provider about other guidelines for travel abroad.
A Guide to Water Filters and Bottled Water
Filtering tap water:
Many, but not all available home water filters remove Cryptosporidium.
Some filter designs are more suitable for removal of Cryptosporidium than others. Filters
that have the words "reverse osmosis" on the label protect against Cryptosporidium. Many
other types of filters that work by micro-straining also work. Look for a filter that has
a pore size of 1 micron or less. This will remove microbes 1 micron or greater in diameter
(Cryptosporidium, Giardia). There are two types of these — "absolute 1 micron" filters and
"nominal 1 micron" filters. The absolute 1 micron filter will more consistently remove
Cryptosporidium than a nominal filter. Some nominal 1 micron filters will allow 20% to
30% of 1 micron particles to pass through.
NSF-International (NSF) does independent testing of filters to determine if they remove
Cryptosporidium. To find out if a particular filter is certified to remove Cryptosporidium,
you can look for the NSF trademark plus the words "cyst reduction" or "cyst removal" on the
product label information. You can also contact the NSF at 789 N. Dixboro Road, Ann Arbor,
MI 48105 USA, toll free1-877-867-3435, fax 313-769-0109, email firstname.lastname@example.org, or visit their
Web site at www.nsf.org/certified/DWTU/. At their Web site, you can enter the model number
of the unit you intend to buy to see if it is on their certified list, or you can look
under the section entitled "Reduction claims for drinking water treatment units - Health Effects"
and check the box in front of the words "Cyst Reduction." This will display a list of filters
tested for their ability to remove Cryptosporidium.
Because NSF testing is expensive and voluntary, some filters that may work against
Cryptosporidium have not been NSF-tested. If you chose to use a product not NSF-certified,
select those technologies more likely to reduce Cryptosporidium, this includes filters with
reverse osmosis and those that have an absolute pore size of 1 micron or smaller.
Note: Filters collect germs from water, so someone who is not HIV infected or immune impaired
should change the filter cartridges. Anyone changing the cartridges should wear gloves and wash
hands afterwards. Filters may not remove Cryptosporidium as well as boiling does because even
good brands of filters may sometimes have manufacturing flaws that allow small numbers of
Cryptosporidium to get in past the filter. Selection of NSF-Certified filters provides additional
assurance against such flaws. Also, poor filter maintenance or failure to replace the filter
cartridges as recommended by the manufacturer can cause a filter to fail.
Labels reading "well water," "artesian well water," "spring water," or "mineral water"
do not guarantee that the water does not contain crypto. However, water that comes from protected
well or protected spring water sources is less likely to contain crypto than bottled water or tap
water from less protected sources, such as rivers and lakes.
You can remove crypto and other germs from your water with a home distiller.
If you use one, you need to carefully store your water as recommended for storing purified water.
Soft drinks and other beverages may or may not contain crypto. You need to know
how they were prepared to know if they might contain crypto.
Crypto killed or removed in preparation
Crypto may not be killed or removed in preparation
Canned or bottled
soda, seltzer, and fruit drinks
Steaming hot (175 degrees F or hotter) tea or coffee
drinks you mix with tap water from frozen concentrate
tea or coffee
Juices made from fresh fruit can also be contaminated with crypto. Several people became ill
after drinking apple cider made from apples contaminated with crypto. You may wish to avoid
unpasteurized juices or fresh juices if you do not know how they were prepared.
Note: This fact sheet is part of a larger publication adapted
from U.S. CDC publication:
Center for Disease Control Division of Parasitic Diseases and U.S. EPA publication: EPA National Primary Drinking Water Regulations..
This fact sheet is for information only and is not meant to be used for self-diagnosis
or as a substitute for consultation with a health care provider. If you have any questions
about the disease described above or think that you may have a parasitic infection, consult
a health care provider.