Cryptosporidium Fact Sheet


Cryptosporidiosis (or “Crypto” for short) is a disease that causes watery diarrhea. Crypto is caused by a microscopic parasite called Cryptosporidium. Anyone can get sick with Crypto, but people with weakened immune systems are more likely to have severe and potentially life-threatening symptoms. This includes people who have health problems or take medicines that lower their body’s ability to fight germs and sickness—such as people whose immune systems are weakened because of cancer, an organ transplant or have cancer, or HIV.

Who is affected?

On Sept. 28, a minimal amount of cryptosporidium was detected in a routine test of the water in the Druid Lake Reservoir conducted by Baltimore City Department of Public Works. This detection impacted only a portion of the Baltimore region water system, in Baltimore City, Baltimore County, and Howard County. Further test results and information can be found here​.

Although Crypto can infect all people, some groups are likely to develop more serious illness:

People with severely weakened immune systems are at risk for more serious disease. Examples of people with weakened immune systems include those with HIV/AIDS; those with inherited diseases that affect the immune system; and cancer and transplant patients who are taking certain immunosuppressive drugs.

Those with immunocompromising conditions are advised to:

  • Drink bottled water
  • Boil water for one minute before consuming
  • Filter tap water using a filter labeled to ANSI/NSF 53 or 58 standards, or a filter designed to remove objects 1 micron or larger. These may be labeled “absolute 1 micron.” (i.e., not Brita-type filters)

What are the symptoms of cryptosporidiosis?

Symptoms of Crypto generally begin 2 to 10 days (average 7 days) after becoming infected with the parasite. Symptoms include:

  • Watery diarrhea
  • Stomach cramps or pain
  • Dehydration
  • Nausea
  • Vomiting
  • Fever
  • Weight loss
Symptoms usually last about 1 to 2 weeks (with a range of a few days to 4 or more weeks) in people with healthy immune systems.

The most common symptom of cryptosporidiosis is watery diarrhea. Some people with Crypto will have no symptoms at all.

What should I do if I think I might have cryptosporidiosis?

For diarrhea whose cause has not been determined, the following actions may help relieve symptoms:

  • Drink plenty of fluids to remain well hydrated and avoid dehydration. Serious health problems can occur if the body does not maintain proper fluid levels. For some people, diarrhea can be severe resulting in hospitalization due to dehydration.
  • Maintain a well-balanced diet. Doing so may help speed recovery.
  • Avoid beverages that contain caffeine, such as tea, coffee, and many soft drinks.
  • Avoid alcohol, as it can lead to dehydration.
Contact your health care provider if you suspect that you have cryptosporidiosis.

Infants, young children,and pregnant women may be more likely than others to suffer from dehydration. Losing a lot of fluids from diarrhea can be dangerous—and especially life-threatening in infants. These people should drink extra fluids when they are sick. If you are pregnant or a parent and you suspect you or your child are severely dehydrated, contact a health care provider.

What is the treatment for cryptosporidiosis?

Over-the-counter anti-diarrheal medicine might help slow down diarrhea, but a health care provider should be consulted before such medicine is taken.

A drug called nitazoxanide has been FDA-approved for treatment of diarrhea caused by Cryptosporidium in people with healthy immune systems and is available by prescription. Consult with your health care provider for more information about potential advantages and disadvantages of taking nitazoxanide.

Individuals who have health concerns should talk to their health care provider.

What precautions should immunosuppressed and take when showering or brushing teeth?

  • Be careful not to swallow any water when bathing or showering.

  • Brush teeth with boiled or bottled water. Do not use tap water that you have not boiled first.​

What should I do if I think my pet has cryptosporidiosis?

A variety of animals, including dogs and cats can get infected with cryptosporidiosis. It is spread to animals when pets swallow food or water contaminated with the parasite, or from the environment contaminated with the poop.

Cryptosporidium infection in dogs and cats is rare; however, if they are affected by the parasite, diarrhea and dehydration are the primary symptoms. If you suspect that your pet is ill with cryptosporidiosis, seek medical care from a veterinarian.

Properly dispose of your pet's waste. Wash your hands with soap and water after contact with or cleaning after your pet.

My business provides water to customers. Should I take any precautions?

Make customers aware of the alert by posting entrances with signage. The notice should detail who is at risk and needs precautions. If your business has implemented additional measures, such as installing water filters and/or using bottled water, share this information with your customers. Food service facilities that serve at-risk individuals should consult their local health department for additional measures.

For childcare facilities, the CDC provides this guidance if a boil water order is issued.

What precautions should healthcare facilities take?

For acute care hospitals, long term care facilities, and dialysis centers, in the event of a boil water advisory, CDC provides this guidance ( for healthcare facilities, this guidance for dialysis centers  (, and this guidance about safe water use in dialysis ( If your facility is located within the affected area, you may want to consider implementing precautions for some or all of your patient population.​​