Cryptosporidium is a parasite that occurs in most countries worldwide and is found in water, food, soil or on any surface contaminated with animal or human faeces. Cryptosporidium can also contaminate lakes, rivers, streams and swimming pools. Contaminated food, especially raw milk, unwashed salads or vegetables and fresh produce can also be a risk.

You can become infected directly from an animal or another person by contact with their infected faeces, for example when changing a nappy or petting an animal and then putting your unwashed hands near/in your mouth. Swimming in and swallowing contaminated water is also a risk.

In the United Kingdom (UK), about 20% of cases are linked to recent foreign travel, with research suggesting many UK cases are associated with visiting Mediterranean countries in mainland Europe. It is most common in children aged between one and five years old, but can affect any age group.

Infection causes an unpleasant diarrhoeal illness called cryptosporidiosis. Symptoms include frequent watery diarrhoea, fever, stomach cramps, appetite loss, and sickness and/or vomiting. Infection can cause dehydration and weight loss. The illness usually lasts about two weeks, but can be longer, especially in people who are immunosuppressed (weakened immune system) who can become seriously unwell.

Cryptosporidium is highly infectious. The parasite is resistant to chlorine and alcohol-based hand sanitisers. Washing hands at key times with soap and water is the best way to help prevent infection.

If you think you are infected, you must be very careful with hygiene for at least 48 hours after your symptoms stop. You are infectious while you are ill and have symptoms and can also pass cryptosporidium in your faeces for several weeks, even if you no longer have symptoms.

See the UK Health Security Agency: Cryptosporidium: public advice for more information about how to protect yourself and your family.

There is no specific treatment for cryptosporidiosis, most healthy people will recover after about a month.

There is no vaccine to prevent cryptosporidium.


You can reduce your risk by

  • washing your hands thoroughly with soap and warm water:
  • before preparing and eating food.
  • after handling raw food.
  • after going to the toilet or changing a baby's nappy.
  • after working with, feeding, grooming or playing with any animals.

Always wash and/or peel fruits and vegetables before eating them.

Do not drink untreated water or unpasteurised milk or eat any unpasteurised dairy product.

Do not have ice or drink/brush your teeth with tap water in countries where the water could be unsafe.

Avoid swallowing water in lakes and swimming pools.

Do not go swimming or take your child swimming while suffering from diarrhoea and for two weeks until after diarrhoea has stopped.

Pay special attention to hygiene during farm visits, washing hands after any contact with animals and only eat or drink in designated areas.

Help children wash their hands properly.


First published : 22 November 2018 Last updated : 11 January 2024

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