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BackFact Sheet
Preventing Cryptosporidiosis:
A Guide to Water Filter and Bottled Water

Preventing Cryptosporidiosis:


Filtering tap water:  

Not all available home water filters remove crypto. All filters that have the words "reverse osmosis" on the label protect against crypto. Some other types also work, but not all filters that remove objects 1 micron or larger from water are the same. Look for the words "absolute 1 micron." Some "1 micron" and most "nominal 1 micron" filters will not work against crypto. To find out if a particular filter removes crypto, contact NSF International (3475 Plymouth Road, P.O. Box 130140, Ann Arbor, MI 48113-0140, 1-800-673-8010, 1-313-769-0109 [fax]), an independent testing group. Ask NSF for a list of "Standard 53 Cyst Filters." Check the model number on the filter you intend to buy to make sure it is exactly the same as the number on the NSF list. Look for the NSF trademark on filters, but be aware that NSF tests filters for many different things. Also look for the words "Standard 53" and the words "cyst reduction" or "cyst removal" for an NSF-tested filter that works against crypto. Because NSF testing is expensive, many filters that may work against crypto have not been tested. Reverse osmosis filters work against crypto whether they have been tested by NSF or not. Many other filters not tested by NSF also work if they have an absolute pore size of 1 micron or smaller.

If you choose to buy a filter, look for this information on the label:

Filters designed to remove crypto
(any of the four messages below on a package label indicate that the filter should be able to remove crypto)

Reverse osmosis (with or without NSF testing)

Absolute pore size of 1 micron or smaller 
(with or without NSF testing)

Tested and certified by NSF Standard 53 for cyst removal

Tested and certified by NSF Standard 53 for cyst reduction


Filters labeled only with these words may not be designed to remove crypto

Nominal pore size of 1 micron or smaller

One micron filter

Effective against Giardia

Effective against parasites

Carbon filter

Water purifier

EPA approved - Caution: EPA does not approve or test filters.

EPA registered - Caution: EPA does not register filters for crypto removal

Activated carbon

Removes chlorine

Ultraviolet light

Pentiodide resins

Water softener

Filters collect germs from water, so someone who is not HIV infected should change the filter cartridges; anyone changing cartridges should wear gloves and wash their hands afterwards. Filters may not remove crypto as well as boiling does because even good brands of filters may sometimes have manufacturing flaws that allow small numbers of crypto to get past the filter. Also, poor filter maintenance or failure to replace filter cartridges as recommended by the manufacturer can cause a filter to fail.

If you drink bottled water, read the label and look for this information:

Water so labeled has been processed by method effective against crypto

Water so labeled may not have been processed by method effective against crypto

Reverse osmosis treated




Filtered through an absolute 1 micron or smaller filter


"One micron absolute"





Ultraviolet light-treated

Activated carbon-treated

Carbon dioxide-treated

Ion exchange-treated




Bottled water 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.

Home distillers: 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.

Other drinks: 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.

If you consume prepared beverages, look for drinks from which crypto has been removed:

Crypto killed or removed in preparation

Crypto may not be killed or removed in preparation

Canned or bottled soda, seltzer, and fruit drinks

Fountain drinks

Steaming hot (175 degrees F or hotter) tea or coffee

Fruit drinks you mix with tap water from frozen concentrate

Pasteurized drinks

Iced 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.


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.

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