logo for quality-drinking-water.com
leftimage for quality-drinking-water.com

Is Cryptosporidium a health concern?

Cryptosporidium also known as crypto, is a parasite that causes Cryptosporidiosis(krip-toe-spo-rid-e-o-sis). It affects the intestines and is typically an acute short-term infection. It is spread through the fecal-oral route, often through contaminated water.

The parasite is protected by an outer shell that allows it to survive outside the body for long periods of time and makes it very resistant to chlorine disinfection.

Despite not being identified until 1976, it is one of the most common waterborne diseases in humans in the United States and is found worldwide.

The following groups have an elevated risk of being exposed to cryptosporidium:

  • People who swim regularly in pools with insufficient sanitation
  • Child care workers
  • Parents of infected children
  • Care takers of other people with cryptosporidiosis
  • International travelers
  • Backpackers, hikers, and campers untreated water
  • People who swallow water from contaminated sources
  • People who handle infected cattle
  • People exposed to human feces through sexual contact

Most people can tolerate small numbers of the parasite in their drinking water with nothing more than a case of diarrhea. However, for people who have weak immune system, such as those with AIDS, cancer and transplant patients who are taking certain immunosuppressive drugs, and those with inherited diseases that affect the immune system, are more at risk.

What are the symptoms of Crypto and how long will it last?

Symptoms include diarrhea, loose or watery stool, stomach cramps, upset stomach, and a slight fever. But some people have no symptoms.

Symptoms will generally begin 2-10 days after being infected and usually last about 2 weeks for those with average immune systems. In some cases the symptoms may go in cycles where you may seem to get better for a few day, then feel worse before the illness ends.

How is Cryptosporidium spread?

Crypto lives in the intestine of infected humans or animals. Millions of Crypto can be released in a bowel movement from an infected human or animal. You can become infected after accidentally swallowing the parasite. Crypto may be found in soil, food, water, or surfaces that have been contaminated with the feces from infected humans or animals. Crypto is not spread by contact with blood.

Crypto can be spread:

  • By putting something in your mouth or accidentally swallowing something that has come in contact with the stool of a person or animal infected with Crypto.
  • By swallowing recreational water contaminated with Crypto. Recreational water is water in swimming pools, hot tubs, Jacuzzis, fountains, lakes, rivers, springs, ponds, or streams that can be contaminated with sewage or feces from humans or animals.
  • By eating uncooked food contaminated with Crypto. Thoroughly wash with uncontaminated water all vegetables and fruits you plan to eat raw. See below for information on making water safe.
  • By accidentally swallowing Cryptosporidium picked up from surfaces (such as toys, bathroom fixtures, changing tables, diaper pails) contaminated with stool from an infected person.

What is the treatment?

There is no effective treatment for this parasite. If you have diarrhea, drink plenty of fluids to prevent dehydration. Rapid loss of fluids because of diarrhea can be life-threatening especially in babies. Parents should consult their health care provider about fluid replacement therapy options for babies. Antidiarrheal medicine may help slow down diarrhea, but consult with your health care provider before taking it.

People poor health or who have a weakened immune system are at higher risk for more severe and more prolonged illness. For persons with AIDS, anti-retroviral therapy that improves immune status will also decrease or eliminate symptoms of infection. Some drugs may reduce the symptoms of Cryptosporidiosis and new drugs are being tested. However, Crypto is usually not cured and may come back if the immune status worsens.

There have been over 24,000 cases of Cryptosporidium infections in the United States in three years. (The most updated information)
  • 2006: 5,936
  • 2007: 11,170
  • 2008: 7,749

There have been many notable outbreaks of Cryptosporidium in the US and around the world.

  • In 1993, a waterborne crypto outbreak occurred in Milwaukee, Wisconsin. An estimated 403,000 people became ill, including 4,400 people hospitalized.
  • The UK's biggest outbreak occurred in Torbay in Devon in 1995 when 575 people fell ill.
  • In the summer of 1996, crypto affected approximately 2,000 people in Cranbrook, British Columbia, Canada. Weeks later, a separate incident occurred in Kelowna, British Columbia where 10,000 to 15,000 people got sick.
  • In April of 2001, an outbreak occurred in the city of North Battleford, Saskatchewan, Canada. Between 5800 and 7100 people suffered from diarrhea illness, and 1907 cases of cryptosporidiosis were confirmed. Equipment failures at the city's antiquated water filtration plant following maintenance were found to have caused the outbreak
  • On September 21, 2007, a crypto outbreak attacked the Western United States: 230 Idaho residents, with hundreds across the Rocky Mountain area; in the Boise and Meridian areas; Utah, 1,600 illnesses; Colorado and other Western states
  • Throughout the Summer of 2008; many public swimming areas, water parks, and public pools in the Dallas/Fort Worth Metroplex of Texas suffered an outbreak of Cryptosporidiosi


Water can be filtered to remove crypto oocysts and the cysts of another protozoan parasite, Giardia lamblia .

Point-of-use filters may be used to treat the water for drinking or preparing foods. Only a water filter with an "absolute" (not "nominal") pore size of one micron or smaller will remove all the crypto in your families drinking water.

Leave Cryptosporidium and go to Quality Drinking Water Home

footer for Drinking Water page