These extra precautions include talking to a health-care provider about boiling drinking water, or using certain drinking water filters, or using certain bottled waters. Cryptosporidium is a parasite commonly found in rivers and lakes, especially when the water is contaminated with sewage or animal waste. For the vast majority of Americans, Cryptosporidium does not pose a grave danger, and the CDC-EPA guidance does not apply to them. However, the guidance does pertain to people with HIV-AIDS, cancer and transplant patients taking immunosuppressive drugs, and people with genetically weakened immune systems. Those who wish to take extra precautions to avoid waterborne cryptosporidiosis can bring their drinking water to a rolling boil for 1 minute.
Boiling water is the most effective approach for killing cryptosporidium.
Only point of use filters that remove particles one micrometer or less in diameter should be considered. 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 varies considerably. Bottled waters derived from protected well and protected spring water sources are less likely to be contaminated by cryptosporidium. Bottled water containing municipal drinking water derived from rivers and lakes are more likely to be contaminated.