The first signs and symptoms of cryptosporidium infection usually appear within a week after infection and may include:

• Watery diarrhea
• Dehydration
• Lack of appetite
• Weight loss
• Stomach cramps or pain
• Fever
• Nausea
• Vomiting

Symptoms may last for up to two weeks, though they may come and go sporadically for up to a month, even in people with healthy immune systems. Some people with cryptosporidium infection may have no symptoms.

Cryptosporidium infection begins when you ingest the one-celled cryptosporidium parasite. Some strains of cryptosporidium may cause more serious disease.

These parasites then travel to your intestinal tract, where they settle into the walls of your intestines. Eventually, more cells are produced and shed in massive quantities into your feces, where they are highly contagious.

You can become infected with cryptosporidia by touching anything that has come in contact with contaminated feces. Methods of infection include:

• Drinking contaminated water that contains cryptosporidium parasites
• Swimming in contaminated water that contains cryptosporidium parasites and accidentally swallowing some of it
• Eating uncooked, contaminated food that contains cryptosporidia
• Touching your hand to your mouth if your hand has been in contact with a contaminated surface or object
• Having close contact with other infected people or animals — especially their feces — which can allow the parasite to be transmitted from your hands to your mouth

If you have a compromised immune system from HIV/AIDS, you're more susceptible to illness from cryptosporidium parasites than is a person with a healthy immune system. People with HIV/AIDS can develop severe symptoms and a chronic, persistent form of disease that may be difficult to treat.

Hardy parasites

Cryptosporidium parasites are one of the more common causes of infectious diarrhea in humans. This parasite is difficult to eradicate because it's resistant to many chlorine-based disinfectants and can't be effectively removed by many filters. Cryptosporidia can also survive in the environment for many months at varying temperatures, though the parasite can be destroyed by freezing or boiling.

People who are at increased risk of developing cryptosporidiosis include:

• Those who are exposed to contaminated water
• Children, particularly those wearing diapers, who attend child care centers
• Parents of infected children
• Child care workers
• Animal handlers
• Those who engage in oral-to-anal sexual activity
• International travelers, especially those traveling to developing countries
• Backpackers, hikers and campers who drink untreated, unfiltered water
• Swimmers who swallow water in pools, lakes and rivers
• People who drink water from shallow, unprotected wells

Complications of cryptosporidium infection include:

• Malnutrition resulting from poor absorption of nutrients from your intestinal tract (malabsorption)
• Severe dehydration
• Significant weight loss (wasting)
• Inflammation of a bile duct — the passage between your liver, gallbladder and small intestine
• Inflammation of your gallbladder, liver or pancreas

Cryptosporidium infection itself isn't life-threatening. However, if you've had a transplant or if you have a weakened immune system, developing complications can be dangerous