Cryptosporidium Explained

Medically Reviewed By Meredith Goodwin, MD, FAAFP
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Cryptosporidium is a microscopic parasite that causes an intestinal infection. The infection results in frequent, watery diarrhea that may last up to a week. Cryptosporidium is the microorganism that causes the diarrheal disease cryptosporidiosis. According to the Center for Disease Control and Prevention (CDC), it affects nearly 750,000 people every year. 

You can get sick with cryptosporidiosis if you eat or drink water contaminated with the cryptosporidium parasite. It is also highly contagious. The CDC also notes that it is the leading cause of waterborne disease outbreaks in the United States.

This article discusses cryptosporidium, the disease it causes known as cryptosporidiosis, symptoms, diagnosis, and the recovery process. 

What is cryptosporidium? 

girls jumping into water
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Cryptosporidium is also often shortened to “crypto.” It is a one-celled parasite that causes a severe diarrheal disease called cryptosporidiosis. This infection is different from cryptococcal meningitis, a fungal infection of the meninges, also called crypto.

Cryptosporidium can survive even in water treated with chlorine because they have outer shells that protect them. They can also survive outside the human body for a long time and can infect animals.

When you have cryptosporidiosis from cryptosporidium, it can cause you to experience many symptoms, such as:

People with healthy immune systems often recover from cryptosporidiosis even without treatment. If you have cryptosporidiosis, your doctor may recommend that you drink lots of fluids to prevent dehydration and eat balanced meals to help relieve symptoms.

What are symptoms that you have cryptosporidium? 

Some people may not experience symptoms immediately after getting the infection from the cryptosporidium parasite. Symptoms often appear in people after 2­–10 days of the infection.

Common symptoms of the infection include:

  • frequent, watery diarrhea
  • nausea and vomiting
  • stomach pain or cramps
  • dehydration
  • weight loss
  • fever

The most common symptom is watery diarrhea. Some people may not even show symptoms at all.

Other people show symptoms that may last for about 1­–2 weeks. People with weaker immune systems may be more likely to get the infection and experience more severe, persistent symptoms.

Read more about diarrhea here.

When should you contact a doctor? 

The cryptosporidium parasite does not cause all diarrhea. Digestive issues, food allergies, or other microorganisms cause some diarrhea. However, contact your doctor if you experience persistent diarrhea. Persistent diarrhea involves 10 episodes or more in 24 hours, which can lead to dehydration.

Also, if other symptoms accompany your diarrhea, like stomach cramps and nausea, reach out to your healthcare professional. 

The following people may have a higher chance of an infection from cryptosporidium:

  • older adults
  • children
  • people who handle animals or who drink untreated water

People with medical conditions that compromise their immune systems, e.g., HIV, often experience more severe symptoms that last for a longer duration.

What causes cryptosporidiosis?

The cryptosporidium parasite causes cryptosporidiosis. The parasite lives in the digestive tracts of humans and animals. However, it can still survive days outside the body. Swallowing the parasite leads to an infection.

One common way of swallowing cryptosporidium is by drinking untreated water. Most waterborne disease outbreaks between 2001 and 2010 linked to cryptosporidium. You can also ingest it by eating contaminated foods or putting contaminated objects into your mouth.

How do you treat cryptosporidium? 

Some people may not need treatment for the infection from cryptosporidium, since it can resolve on its own.

Medications may also help treat the condition. Your doctor can prescribe medications such as nitazoxanide and loperamide to help relieve diarrhea. Loperamide is also available over the counter under the brand name Immodium A-D.

For people with weak immune systems due to medical conditions, doctors may need to treat the underlying condition to strengthen the immune system so it can clear the infection. 

Your doctor may also advise that you drink plenty of water and take oral rehydration powders to help prevent dehydration

How long is the recovery process? 

Many people often recover fast when they get an infection from cryptosporidium. For some, it does not cause symptoms, while others may experience symptoms that can last for days.

People with weak immune systems tend to be at a greater risk because an infection from cryptosporidium can be life threatening.  

Symptom recurrence is possible even after recovery. You can experience symptoms that come and go for up to 4 weeks

Foods to eat when you have cryptosporidium 

If you have an infection from cryptosporidium, it is a good idea to eat foods that can help rehydrate you and to avoid foods that will cause dehydration or worsen your symptoms.

  • Drink plenty of water.
  • Eat balanced meals.
  • Avoid caffeine, alcohol, and foods that trigger nausea or allergy, which can worsen symptoms.

How is cryptosporidium diagnosed? 

Since people with an infection from cryptosporidium shed the parasite in their feces, your doctor will most likely order stool tests, which healthcare professionals perform in a lab. These tests help them look for signs of the parasite. 

They can look at the samples under a microscope. They can also take a DNA test to look for the parasite’s genetic material, or do antigen testing to check for a protein that points to the microorganism causing the issue. 

What are the risks factors for developing cryptosporidium?

People can contract the cryptosporidium parasite by eating and drinking water contaminated with it. The parasite can spread from hand to mouth when you put contaminated hands into your mouth, for example.

Ways to transmit the cryptosporidium parasite include:

  • drinking untreated water, e.g., swallowing recreational swimming water
  • touching animals or contaminated surfaces
  • eating undercooked or raw food contaminated with cryptosporidium
  • having oral or anal sex with someone who has the infection from cryptosporidium
  • touching contaminated toys or diapers

People cannot contract cryptosporidium via blood.

How do you prevent cryptosporidium? 

There is currently no available vaccine for preventing the infection from cryptosporidium. However, some things you can do to prevent infection include washing your hands thoroughly with soap and water when:

  • using the toilet or changing your baby’s diapers
  • touching surfaces without disinfection
  • handling soil
  • preparing meals

There are other tips to prevent infection from cryptosporidium as well:

  • Treat your water properly before drinking.
  • Cook your food, including meat, thoroughly before eating.
  • Wash fruits properly under treated, running water before eating.
  • When traveling internationally, drink treated water or boil the water yourself before drinking.


Infection from cryptosporidium is highly contagious, causing frequent watery diarrhea. Older adults, children, and people with weaker immune symptoms tend to be more likely to get it. However, it is treatable. 

For many people, symptoms last for several days. In rare cases, it can be severe, presenting with symptoms that last for weeks. Your doctor can prescribe the right medication for you after diagnosis. 

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Medical Reviewer: Meredith Goodwin, MD, FAAFP
Last Review Date: 2022 Jul 13
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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