Department of Health

Cryptosporidium

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Key messages

  • Aquatic facilities and the public play an important role in preventing the spread of cryptosporidiosis.
  • Cryptosporidium parvum is a parasite that is highly resistant to the levels of chlorine normally found in swimming pools.
  • Cryptosporidium spreads through faeces and is highly contagious. Do not swim for 14 days after diarrhoea has stopped.

What is Cryptosporidium?

Cryptosporidium parvum is a parasite excreted in the faeces of infected humans, cattle and other mammals. The infection is known as cryptosporidiosis, or sometimes just 'crypto'. It occurs by:

  • accidentally swallowing contaminated pool water
  • drinking contaminated tap water
  • consuming contaminated food
  • directly contacting faeces such as from an infected child's nappies or an infected animal.

C. parvum is highly resistant to the levels of chlorine normally found in swimming pools. One infected person can contaminate a large swimming pool in a single visit, potentially infecting anyone in the water before the chlorine can kill the parasite.

Symptoms

The symptoms are usually mild, but can be more severe in people with weak immune systems, such as children, the elderly and pregnant women. After infection it can take anywhere between one and 12 days for the illness to take hold. On average, symptoms will appear a week after infection. Symptoms may include:

  • profuse, watery diarrhoea, often with abdominal cramping
  • bloating
  • fever
  • loss of appetite
  • fatigue
  • nausea and vomiting.

The symptoms usually last for about two weeks. People with weak immune systems may be ill for longer. Even after recovery, the parasite may be present in faeces for up to two weeks after recovery. To avoid spreading cryptosporidiosis, do not swim during this period. 

If you or your family develop a gastrointestinal illness after swimming at a public pool, contact the pool manager so any potential outbreak can be monitored. 

There is no specific treatment for cryptosporidiosis. Consult your doctor for medical advice.

Reviewed 02 December 2021

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Water Unit

50 Lonsdale Street, Melbourne, VIC 3000
Phone 1300 761 874 (business hours)
water@dhhs.vic.gov.au
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