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Outbreaks from a contagious pathogen called Cryptosporidium have been reported around the world. In 1993, 403,000 people in Milwaukee, USA were infected through contaminated drinking water.

What’s even more distressing is that these active forms of the parasite are HIGHLY RESISTANT to the commonly used chemicals for pool disinfection, namely chlorine and bromine.

Closer to home, in 1998 over 1,000 cases were reported in NSW, Queensland, and the Australian Capital Territory. This time the source of infection was not the drinking water but the water you play in….swimming pools.

Just recently, a warning was issued in January 2017 by NSW Health urging parents to keep their children out of swimming pools and splash parks if they were suffering from diarrhea.

What prompted this warning? Just one month earlier, 149 cases of cryptosporidiosis were diagnosed in the area and half of the cases were children under 10 years old.

What is Cryptosporidium?

For those who manage pool and water park facilities, you are probably aware that Cryptosporidium is a pathogen that poses a serious health risk to the public.

This parasite infects the intestinal tract of humans and causes diarrhea, cramping, nausea, vomiting, and fever.

It is transmitted through the contaminated feces of infected individuals.

Why Is It Spread So Easily

Because of the nature of public water-based facilities, there is an increased risk of contamination mostly due to the significant number of people using the pool.

Swimming pools and water parks become breeding grounds for Cryptosporidium when the water has been contaminated.

The troubling reality is that the parasite can remain active in its infective form for more than ten days. So although the infected individual is no longer in the pool, Cryptosporidium can still survive in the water for a long time.

What’s even more distressing is that these active forms of the parasite are HIGHLY RESISTANT to the commonly used chemicals for pool disinfection, namely chlorine and bromine.

What You Can Do if an Outbreak Occurs at Your Facility

When an outbreak occurs, it can send fear and panic waves through your staff and facility. Stay calm. There are things you can do to eradicate this pathogen from your swimming pool.

Consider the following three ways to manage a Cryptosporidium outbreak once it occurs…

Proper Hygiene

Preventing further contamination is key. Make it known at your facility that patrons who have experienced diarrhea in the past two weeks are prohibited from using the swimming pool or water park.

This is essential to stop the spread of this gastrointestinal illness.

Also, consider the following points to promote proper hygiene:

  • The toilet should be used before swimming
  • Shower with soap and water before using the pool
  • Young children and infants must wear swimming diapers at all times
  • Non-toilet trained babies should only use the toddler pool
  • Diapers should never be changed poolside but instead in the change rooms
  • Avoid swallowing or spouting any of the pool water


Educating your staff and pool patrons is necessary to help them understand how the disease is transmitted and to then take the necessary precautions to avoid spreading it further.

Here are some additional strategies to help educate those involved:

  • Provide posters and pamphlets around your facility;
  • Promote proper personal hygiene by posting appropriate signs in the entryway, toilet doors, shower stations, and hand washing areas;
  • Educate your staff on the protocols involved in exiting patrons from the pool when someone accidently has a fecal accident in the pool;
  • Make it known that the pool management has the right to prevent people from using the pool if they have dirty hygiene practices.

Pool Operations

Barriers are used to stop the transmission of these deadly parasites to the pool patrons. Source control, cleaning and disinfection, and pool closure are techniques used to minimize the risk of further transmission to swimmers.

Let’s look at some of these operational practices when using these barriers:

Ultrafine filtration (UFF)

Has the ability to remove the infective form of Cryptosporidium in the pool.

These filter systems should be operated at full efficiency before, during, and after swimming.

However, it should not be counted on as the ultimate control measure but used in conjunction with other methods of elimination due to the length of time it takes to filter all of the water in the pool and dead spots due to poor circulation.

The toddler wading and hydrotherapy pools should contain its own independent filtration and disinfection systems that do not come in contact with the water in other pools to avoid cross contamination

Be aware that it may takes days or even weeks to kill Cryptosporidium using standard recommended levels of chlorine and bromine, assuming that there has been no further source of contamination. This time delay is insufficient to protect swimmers and so other measures need to be taken in addition to maintaining these levels.

Chlorine shock dosing (Ct shock dosing)

should be used to inactivate these disease-causing pathogens.

Essentially, shock dosing is adding high concentrations of chlorine to the pool over a period of time to achieve a Ct value of 15,300.


Every two weeks during Cryptosporidium outbreaks should be considered. This is usually done overnight when swimmers are not present in the pool.

pH pool levels should be maintained at key guideline levels to ensure safe levels for human contact as well as effective disinfection.

Although, the risk of disease and contamination is always present in public pools, fast and effective action is key in bringing Cryptosporidium outbreaks under control.


Cryptosporidium outbreaks trigger warnings for pools & patrons in Australia

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