Medically Reviewed by Jonathan E. Kaplan, MD on May 29, 2024
6 min read

Cryptosporidium is a tiny one-celled parasite that can make you sick. When you have a cryptosporidium infection, your doctor might call it cryptosporidiosis. Both the germ and the illness are also called crypto. It can happen in people who have advanced HIV, or AIDS.

It’s different from cryptococcal meningitis, a fungal infection that AIDS patients can get, which may also be called crypto.

Some people who get crypto don’t have symptoms. Others may have:

Symptoms may begin 2 to 10 days after infection. They usually last 2 weeks or more.

The parasite can be in your poop for up to 2 months. During this time, you can spread it to other people.

Crypto parasites live in the intestines of humans and animals. Swallowing as few as 10 of them can cause an infection.

You can get crypto by:

  • Putting something in your mouth after it’s touched poop from a person or animal that has crypto
  • Touching your mouth after touching an infected person’s or animal’s poop
  • Touching your mouth after touching contaminated dirt or objects
  • Swimming in or drinking contaminated water
  • Eating contaminated food

Cryptosporidiosis isn’t spread through contact with blood.

You’re more likely to get a crypto infection if you:

  • Work at or attend a day-care center
  • Have an infected child
  • Care for people who have crypto
  • Are age 75 or older
  • Travel internationally
  • Drink unfiltered, untreated water, such as from shallow, unprotected wells
  • Swim in pools, lakes, or rivers
  • Handle infected animals
  • Have contact with poop through sex

Who is most at risk of severe illness?

People who have a weakened immune system are most likely to get severe crypto. This includes those who have AIDS, who have other diseases that affect their immune system, or who are taking certain medications because of cancer or an organ transplant. In these people, crypto infection can be serious, long-lasting, and sometimes deadly.

If your CD4 cell count (a type of white blood cell affected by HIV) is below 200, you’re more likely to have diarrhea and other crypto symptoms for a long time.

If your CD4 count is above 200, you’ll probably have symptoms for only a few days or weeks. But the parasites could still hide in your intestines. They could cause problems again if your CD4 count drops below 200.

Your doctor will look for signs of the parasite in one or more samples of your poop. They might do tests such as:

  • Antigen testing to check for a certain protein
  • DNA tests to look for crypto’s genetic material
  • Looking at the samples under a microscope

If you have diarrhea that isn’t going away and tests don’t show a cause, you may need an endoscopy. Your doctor uses a thin, flexible tube called an endoscope to look at the upper part of your digestive tract. They might also take a tissue sample.

For people who have advanced HIV, or AIDS, the most important treatment is antiretroviral therapy (ART). It fights the virus and helps your immune system work better.

In the meantime, diarrhea can make you dehydrated, so drink plenty of fluids. Oral rehydration powders can also help. Talk to your doctor before taking any medicine.

Depending on your case, your doctor might recommend medications such as:

If you have a healthy immune system, you’ll probably get better on your own.

In addition to dehydration, the complications of crypto may include:

  • Poor nutrition, which might lead to slow development in children
  • Bile duct or pancreas conditions
  • Respiratory problems


If you have HIV, the most important thing is to start ART early, before it becomes AIDS. People with CD4 counts higher than 200 rarely have serious problems with crypto.

Some other steps can reduce your risk of getting crypto. They’ll also help protect you against other diseases.

Wash your hands. Doing this often with soap and water is probably the most important thing you can do to stay healthy. Always wash your hands before preparing or eating food. Wash well after:

  • Touching children in diapers
  • Touching clothing, bedding, toilets, or bedpans used by someone who has diarrhea
  • Gardening
  • Touching pets or other animals
  • Touching anything that might have had contact with human or animal poop, including dirt in your garden

Even if you wear gloves when you do these things, wash your hands well when you finish. Make sure children do the same.

Practice safe sex. Infected people can have crypto on the skin around their genitals and anus, including the thighs and buttocks. Because it’s hard to tell if someone has crypto, be careful with any partner: Avoid rimming (kissing or licking the anus). It’s very likely to spread infection, even after washing. Always wash your hands well after touching your partner's anus.

Avoid touching farm animals. If you touch a farm animal, especially a young one, or visit a farm where animals are raised, wash your hands well with soap and water before preparing food or putting anything in your mouth. Don’t touch animal poop. Wear disposable gloves while cleaning your shoes, and wash your hands after taking off the gloves.

Avoid touching pet poop. Though most pets are safe, someone who has a healthy immune system should clean cages or litter boxes. Wear disposable gloves when cleaning up after a pet, and wash your hands afterward. The risk of getting crypto is highest from pets that are less than 6 months old, animals that have diarrhea, and stray animals. If you get a puppy or kitten that’s younger than 6 months, have it tested for crypto before bringing it home. If any pet gets diarrhea, have it tested for crypto.

Don’t swallow water when swimming in lakes, rivers, or pools, or when using hot tubs. The chlorine in swimming pools and water parks doesn’t kill the parasites. Crypto can also live in fresh and salt water for several days.

Wash and/or cook your food. Fresh vegetables and fruits may have crypto on them. If you’re going to eat them raw, wash them well first. Then peel them if you can. Don’t eat or drink unpasteurized milk or dairy products.

Drink safe water. Don’t drink directly from lakes, rivers, streams, or springs. Tap water in the U.S. is generally safe, but you might not want to use it, including water and ice from a refrigerator icemaker. Check with your local health department and water utility to see if they’ve issued special notices for people with weakened immune systems. You might also want to boil your water, filter it, or drink certain types of bottled water. Look for filters that say “reverse osmosis,” “absolute 1 micron,” “cyst reduction,” or “cyst removal” on the label. Processed carbonated (bubbly) drinks in cans or bottles are probably safe, but drinks made at a fountain might not be, because they use tap water. Follow public health department advisories about boiling water.

Take extra care when traveling. Some places have poor water treatment and food sanitation. Avoid raw fruits and vegetables, tap water or ice made from tap water, unpasteurized milk or dairy products, and things from street vendors. Steaming-hot foods, fruits you peel yourself, bottled and canned processed drinks, and hot coffee or tea are probably safe.