Department of Health

Continued increase in cryptosporidiosis cases across Victoria

Health advisory

Advisory number:
Date issued:
19 Mar 2024 - (update to alert issued on 20 Dec 2023)
Issued by:
Dr Clare Looker, Chief Health Officer
Issued to:
Victorian public and health professionals

Key messages

  • The number of cryptosporidiosis (crypto) cases in Victoria remains high. Last week Victoria received the highest number of reported cases for this season.
  • Many cases have become infected after using public swimming pools, and public health investigations have found people are attending pools while they are infectious.
  • Health professionals should consider the possibility of cryptosporidiosis in people presenting with gastroenteritis, ask about exposures in the previous two weeks, provide infection control and exclusion advice, and notify the department of all positive cases.
  • People with known cryptosporidiosis or an unknown cause of diarrhoea should not swim while they have diarrhoea and for a full two weeks after their diarrhoea stops. This avoids contaminating the pool water and the risk of transmission to others.

What is the issue?

Cryptosporidiosis is a type of gastroenteritis (gastro) caused by the parasite Cryptosporidium.

There has been a significant increase in cryptosporidiosis cases in Victoria since the beginning of September 2023, with the highest weekly number of cases (87) notified last week. This year there has been 607 reported cases, over 600% higher than the 84 cases notified in the same period in 2023. Many cases are linked to swimming in public pools.

Cryptosporidium parasites are highly resistant to the levels of chlorine normally found in swimming pools.

Outbreaks associated with pools occur when people attend a pool with a Cryptosporidium infection. Swimmers can become infected when they accidentally swallow pool water contaminated with the parasite.

Who is at risk?

All people can become infected. In Melbourne, the risk appears to be greatest for those exposed to swimming pools such as young children who attend swimming lessons with other children and who are more likely to swallow pool water, or for those who are household contacts of cases. Although most illness is mild and self-limiting, certain groups are more at risk of severe illness if infected, including younger children, pregnant women and people with weakened immune systems.

Symptoms and transmission

The most common symptoms of cryptosporidiosis are watery diarrheoa and stomach cramps which may last several weeks. It can be spread to others both during the illness, and for up to two weeks after symptoms resolve.

Other symptoms may include fever, nausea, vomiting, bloating and loss of appetite. Less commonly, cryptosporidiosis can present as pneumonia, cholecystitis or pancreatitis. Some people who are infected may not show any symptoms.

Transmission of cryptosporidiosis occurs by the faecal-oral route (when the parasites are taken in by mouth). This can happen directly through eating contaminated food and water or, more commonly, from person to person or animal to person. Outbreaks can be linked to sources such as contaminated drinking water, swimming pools and petting infected animals.

The typical incubation period is around 1 to 12 days, with an average of 7 days. Cases are infectious while they excrete the parasite - an infected person typically excretes Cryptosporidium while symptomatic and for up to two weeks after the diarrhoea has stopped. For this reason, it is important that people with cryptosporidiosis do not swim for 14 days after diarrhoea ceases.


For the public

  • Do not swim if you have had cryptosporidiosis or diarrhoea of unknown cause in the past 14 days.
  • Shower and wash with soap, especially the bottom, before swimming.
  • Avoid swallowing pool water.
  • Wash hands with soap after going to the toilet, changing a nappy, handling animals or before preparing food or drink.
  • Do not handle food or prepare food for others until at least 48 hours after diarrhoea has stopped.
  • Change nappies in nappy change areas only.
  • Keep children home from childcare or school until 24 hours free of symptoms.
  • If you think you or your child may have cryptosporidiosis, contact your doctor who will ask you for a stool (faeces or ‘poo’) sample for testing. If the results of the tests show that you have cryptosporidiosis, the doctor will be able to provide you with advice and will also notify the Department of Health.

For health professionals

  • All patients with gastroenteritis who used a public swimming pool in the two weeks prior to symptom onset should be considered for cryptosporidiosis and education provided on reducing transmission.
  • Send a stool sample requesting testing for Cryptosporidium, and any other relevant investigations for gastroenteritis.
  • Provide education on reducing transmission to all patients with cryptosporidiosis. This includes strongly advising patients not to swim for two weeks after symptoms have resolved.
  • Provide advice about the importance of hand hygiene measures and if relevant, advise exclusion from childcare settings until the patient has 24 hours free of symptoms.
  • Cryptosporidiosis is a routine notifiable condition under the Public Health and Wellbeing Regulations 2019 and requires written notification by medical providers and pathology services within five days of diagnosis.

Where to get help:

Reviewed 20 March 2024

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