AIDS: The Centers for Disease Control and Prevention (CDC) recommends that immunocompromised people avoid exposure to cryptosporidium in outbreak settings by drinking water that is boiled, filtered, or bottled. A parasite, cryptosporidium is spread when persons ingest infected feces of humans or animals, or eat raw or undercooked vegetables contaminated with an egg-like form of the parasite. Symptoms include watery diarrhea, headache, abdominal cramps, nausea, vomiting and low-grade fever; in immunocompromised patients infection often leads to weight loss, dehydration, and may become life-threatening. Drugs can treat the symptoms, although cryptosporidiosis is not curable and often recurs in severely immunocompromised patients. To prevent becoming infected; HIV-positive people should not drink water from lakes, rivers, and swimming pools; avoid unpasteurized milk or milk products; wash hands after contact with pets or with soil; and follow safe-sex guidelines. The CDC also recommends that in settings with an outbreak of cryptosporidium, individuals boil water for one minute to kill the parasite or use a filter for tap water that is capable of removing particles less than one micron in diameter. A third option is to use bottled water for drinking, although it is difficult to know which is safe since no organization regulates it.