Anyone who has had diarrhoea recently is being urged to stay out of the pool to avoid spreading a parasitic illness.
NSW Health has urged those who have had diarrhoea not to go swimming for at least two weeks afterwards.
The disease, cryptosporidiosis, is caused by a parasite that infects the intestine and is most well-known for causing watery diarrhoea and stomach cramps.
The disease can also cause fever, nausea, vomiting and loss of appetite, though none is guaranteed.
It is a common cause of acute diarrhoea in young children, particularly under ten years old.
Executive Director, Health Protection NSW, Dr Jeremy McAnulty said people typically get the disease by swimming in and swallowing water containing these parasites, called Cryptosporidium.
This can include swimming pools where multiple children will be spending time in the same water.
“The parasite survives for many days, even in chlorinated pools, and in the past very large outbreaks have been caused by people who had recently been infected going swimming,” Dr McAnulty said.
“Almost half of the cases reported this year had been swimming during their exposure period, and with such a high proportion of young children affected and with many schools about to hold swimming carnivals, we’re urging parents to stay alert for symptoms”.
In 2024, NSW has seen 498 reported cases of cryptosporidiosis so far. The same time period has a five-year average of 95 cases, making this a steep increase.
Queensland’s cryptosporidiosis cases are even greater, with more than 823 recently recorded infections compared to January 2023’s 56 cases.
NSW Health advised that once the symptoms resolve, those with diarrhoea should also avoid sharing towels for two weeks and handling food for 48 hours. Children should also stay away from schools and areas with other kids for 24 hours after the diarrhoea has stopped.
To avoid catching the disease, people should wash their hands thoroughly and regularly, avoid swallowing water and avoid swimming in waterways and beaches after heavy rain.
Boiling water is a method of effectively killing the Cryptosporidium parasite.
More information can be found on the NSW Health website.