CDC, EPA issue drinking water guidance for people with weakened immune systems.

June 15, 1995. The Centers for Disease Control and Prevention (CDC) and the Environmental Protection Agency (EPA) recently issued guidance to people with severely weakened immune systems who may want to take extra precautions to reduce the risk of infection with Cryptosporidium from drinking water.

The CDC-EPA guidance suggests that immunosuppressed individuals discuss their risks with their healthcare provider. Those who wish to take extra precautions to avoid waterborne cryptosporidiosis can bring their drinking water to a rolling boil for one minute. Boiling water is the most effective approach for killing Cryptosporidium, according to CDC-EPA.

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. Among the most effective point-of-use filters are those labeled reverse osmosis or "Absolute" one micrometer filters or those labeled as certified by NSF International under Standard 53 for "Cyst Removal." The "Nominal" one micrometer filter rating is no/standardized and many filters in this category may not reliably remove Cryptosporidium.

* Bottled water. Many, but not all, brands of bottled water may provide a reasonable alternative to boiling tap water. However, the origin of the source water, the types of microorganisms in that water, and the treatment of that water before it is bottled vary considerably. Bottled waters derived from protected well and protected spring water sources are less likely to be contaminated by Cryptosporidium than bottled waters containing municipal drinking water derived from less protected sources such as rivers and lakes. Any bottled water treated by distillation or reverse osmosis before bottling assures Cryptosporidium removal.

Neither EPA nor CDC maintains a list of point-of-use filters or bottled water brands that meet the above criteria. NSF International can provide a list of filters that meet the NSF criteria. The NSF address is 3475 Plymouth Road, P.O. Box 130140, Ann Arbor, Michigan 48113-140; phone number: 1-800-NSF-8010. Individuals who contact bottlers or filter manufacturers for information should request data supporting claims that a brand of bottled water or filter can meet the above criteria. For more information on bottled water, contact the International Bottled Water Association's Hotline at 1-800-WATER-11.

CDC and EPA will continue to assess the risks of waterborne cryptosporidiosis and will report new information as it is developed. Individuals concerned about the threat of cryptosporidiosis in tap water can call CDC's National AIDS Hotline [phone]-AIDS).