reports that the six children living in a well-defined, relatively small corner of Belgium, Wisconsin who were infected with E. coli O157:H7 had related infections with other dangerous bugs, including Cryptosporidium and Clostridium difficile. 

Cryptosporidium parvum (also known as "Crypto") is a parasite that is too small to be seen with the naked eye. It is found in water and food sources contaminated with the feces of infected humans, cattle, and other mammals. The infectious form of the parasite, known as an "oocyst," is highly resistant to the levels of chlorine normally found in drinking water and swimming pools.

Symptoms of Cryptosporidium

Cryptosporidiosis, the infection caused by ingestion of the Cryptosporidium parasite, causes painful abdominal cramping and profuse, watery diarrhea. In addition to diarrhea, symptoms of infection are fatigue, fever, nausea, vomiting, and loss of appetite.

Symptoms of Cryptosporidiosis appear an average of seven days after oocysts are swallowed, and normally last for two weeks or less in healthy adults. People with compromised immune systems (those with diabetes, receiving cancer treatments, who have received organ transplants, or are infected with HIV/AIDS), the elderly, pregnant women, and small children are more likely to become infected, and will suffer more severe illnesses than healthy adults. In some cases, Cryptosporidiosis can be life-threatening, especially when those infected become dehydrated.

Detection and Treatment of Cryptosporidium

Infection with Cryptosporidium parvum typically occurs after a person swallows contaminated water, eats contaminated food, or comes into direct contact with contaminated feces. Since 1988, health departments have documented more than ten outbreaks traced to contaminated water sources, including water parks and swimming pools in the U.S. Thousands have become ill.

The number of Cryptosporidium oocysts needed to cause human infection is relatively low — ingestion of as few as two to ten oocysts can cause illness. When infectious, a person can pass millions of oocysts per day in his or her stool; even after symptoms resolve, a person can remain infectious for a number of weeks. Therefore, it is important that individuals experiencing symptoms of diarrheal illness do not participate in activities that could lead to the contamination of water (i.e. swimming in pools, playing in spray-or waterparks).

Cryptosporidium may remain infectious for 2-6 months in moist environments outside the body.

Prevention of Cryptosporidium

Reported outbreaks of Cryptosporidium are small in number, but it is believed that as physicians and other health care providers increase their testing of patients with diarrheal illness for crypto that reported incidence will increase. Once a pool is contaminated by fecal accident or by rinsing a diaper in the water, it can remain a source of infection for significant periods of time since Cryptosporidium is resistant to treatment with Chlorine.

In addition to its resistance to treatment with Chlorine, Cryptosporidium is difficult to filter out of water sources because the oocysts are microscopic in size. Oocysts can pass through pool sand filters and most cartridge filters relatively easily; however, a diatomaceous earth filter can capture most oocysts.