What is Cryptosporidium?
Cryptosporidium is a parasite that causes an illness called cryptosporidiosis or "crypto." People can get it by swallowing food or water that has the parasite in it, or by touching surfaces or being around people who are infected.
Crypto is the most common cause of water‑related disease outbreaks. The main symptom is watery diarrhea, but it can also cause stomach pain, dehydration, nausea, vomiting, fever, weight loss, or sometimes no symptoms at all. Symptoms usually start 2 to 10 days after someone is infected. In people with healthy immune systems, the illness usually lasts one to two weeks but can come and go for up to a month. If you have been diagnosed with crypto, stay out of the water for two more weeks after your diarrhea stops.
Most people recover without treatment. However, people with weakened immune systems may get more serious or long‑lasting illness and may need medical care. Anyone with diarrhea—especially young children and pregnant women—should drink plenty of fluids to prevent dehydration.
Cryptosporidium in Pools
Crypto is most often spread through swimming water and drinking water. It can survive in a properly chlorinated pool for more than 11 days because it has a tough outer shell. Here are some ways to help prevent the spread of crypto:
- Do not go in the water if you have diarrhea
- If you have been diagnosed with Crypto, stay out of the water for an additional two weeks after diarrhea stops
- Shower before entering the water (the pool is only as clean as you are!)
- Do not pee or poop in the water
- Do not swallow the water
- Every hour:
- Take kids for a bathroom break
- Check diapers and change them (but not poolside)
- Check the free chlorine level and pH before entering the water
- Pools should have 1-3 mg/L or parts per million (ppm) of free chlorine and a pH of 7.2-7.8
- Hot tubs and spas should have 2-4 ppm of chlorine or 4-6 ppm of bromine and a pH of 7.2-7.8
- You can find pool test strips at most superstores, hardware stores, and pool supply stores.
Crypto can live in chlorinated water for more than 10 days, so the best way to prevent infection is to keep it out of the water in the first place. This can be accomplished by following a few simple rules, which should be posted for patrons to see.
- Maintain pools, lakes, and other recreational water venues to standards set by local or state laws.
- Maintaining pools and splash pads with proper chlorine level (at least 1 part per million or ppm) and pH (7.2–7.8) is the first defense against the spread of most germs.
- Don’t swim or let kids swim if sick with diarrhea. This includes aquatics staff.
- Keep patrons and staff diagnosed with crypto out of the water for an additional two weeks after diarrhea stops. People infected with crypto can typically continue to shed crypto for up to two weeks after diarrhea completely stops.
- Promote handwashing and frequent bathroom breaks.
1. Close the pool
If you have multiple facilities that use the same filtration system, all facilities will need to be closed.
2. Remove the fecal matter
Use a net or bucket and be sure to sanitize it after use. (*Vacuuming fecal matter is not recommended)
3. Maintain conditions
pH should be kept at or below 7.5.
4. Raise the chlorine levels
If the feces is solid, raise the chlorine to 2ppm for 25-30 minutes. Times and levels may vary based on site conditions. Contact your local health department for more information.
If the feces is diarrhea and there is not chlorine stabilizer, raise the chlorine to 10 ppm for 25.5 hours or to 20 ppm for 12.75 hours.
If the feces is diarrhea and there is chlorine stabilizer, raise the chlorine to 20 ppm for 28 hours or 30 ppm for 18 hours or 40 ppm for 8.5 hours.
5. Check filtration
Ensure that the filtration system is operating while water is brought to and maintained at the appropriate chlorine and pH levels.
6. Backwash the filter (for diarrhea only)
Discharge directly to waste, do not return the backwash through the filter.
7. Allow swimmers back in the water.
After ensuring that chlorine and pH are back to normal operating levels.
More Information
Visit the CDC for more information on What to do when there is poop in the pool 
. The Mini-Model Aquatic Health Code on Reducing the spread of Cryptosporidium provides detailed information on how to treat water to reduce crypto.
Contact your local health department in the event of a fecal accident - they can help provide guidance on pool management and water remediation.