A growing number of cases of a diarrheal illness caused by the parasite Cryptosporidium—often called Crypto—have been reported across parts of the United States. While the infection is usually mild in healthy people, it can cause severe illness in young children, older adults, and individuals with weakened immune systems.
Here’s what you should know about this parasite, how it spreads, its symptoms, and how you can protect yourself and your family.
What Is Cryptosporidium?
Cryptosporidium is a microscopic parasite that infects the intestines and causes an illness known as cryptosporidiosis. It is one of the most common causes of waterborne diarrheal disease worldwide.
The parasite produces a protective outer shell that allows it to survive for days—even in properly chlorinated swimming pools—making it highly contagious.
How Does It Spread?
People become infected after swallowing the parasite. Common sources include:
- Drinking contaminated water
- Swimming in contaminated pools, lakes, or water parks
- Eating contaminated food
- Contact with infected people, especially during diaper changes
- Contact with infected farm animals
Even tiny amounts of contaminated water or food can transmit the infection.
Symptoms
Symptoms usually begin 2 to 10 days after exposure and may include:
- Frequent watery diarrhea
- Stomach cramps
- Nausea
- Vomiting
- Low-grade fever
- Dehydration
- Loss of appetite
- Weight loss
Most healthy adults recover within 1 to 2 weeks, although diarrhea can sometimes last longer.
Who Is Most at Risk?
The illness can be more serious for:
- Children under 5
- Adults over 65
- Pregnant women
- People with weakened immune systems
- Organ transplant recipients
- Individuals receiving chemotherapy
These groups are more likely to experience prolonged or severe diarrhea.
Treatment
There is no instant cure for cryptosporidiosis. Treatment mainly focuses on preventing dehydration.
Doctors often recommend:
- Drinking plenty of fluids
- Oral rehydration solutions
- Rest
- Eating bland foods until symptoms improve
In some cases, a prescription medication called nitazoxanide may be recommended for otherwise healthy individuals.
How to Prevent Infection
Simple hygiene habits can greatly reduce your risk:
- Wash your hands thoroughly with soap and water.
- Avoid swallowing pool or lake water.
- Wash fruits and vegetables before eating.
- Drink safe, treated water when traveling.
- Stay out of swimming pools for at least 2 weeks after diarrhea has completely stopped, since the parasite can still be shed.
When to See a Doctor
Seek medical attention if you experience:
- Severe dehydration
- Bloody diarrhea
- High fever
- Diarrhea lasting more than a week
- Persistent vomiting
- Symptoms in infants, elderly adults, or people with weakened immune systems
The Bottom Line
Although reports of Cryptosporidium infections have increased in some areas, there is no evidence that the entire U.S. is experiencing a nationwide emergency outbreak. The parasite has long been present in the United States, and public health agencies continue to monitor cases.
The best protection is good hand hygiene, safe food and water practices, and prompt treatment of dehydration if illness occurs. Most healthy people recover completely with supportive care, but anyone with severe or prolonged symptoms should contact a healthcare provider promptly.
