WA Health Department issues warning over increase in cases of gastro bug Cryptosporidiosis

WA Health has issued a major health warning after cases of a highly infectious stomach bug linked to swimming pools and water parks flooded authorities at a rate of 70 a week last month.

Cryptosporidiosis cases have skyrocketed in the first two months of this year, with a “significant increase” reported in February, concentrated mainly in the Perth metro area.

There were 291 cases reported to WA Health last month at an average of 70 cases a week — well above the seasonal increase seen in summer in past years.

Almost half of those cases have been in children under 10.

It prompted the Department of Health to on Friday warn people who “have had diarrhoea not to enter any swimming pool, water spray park or other aquatic facility for at least two weeks after they have made a full recovery”.

A severe form of gastroenteritis, crypto is a highly infectious stomach bug caused by the water-borne parasite cryptosporidium.

Symptoms include diarrhoea, stomach cramps and sometimes fever, nausea and vomiting.

It can be easily spread from person-to-person in households, childcare facilities, and via swimming pools or waterparks by swimming in contaminated water, or by consuming infected food.

WA has found itself in the grips of a major outbreak of the reportable illness, with almost 500 cases already this year — more than 60 per cent of the 804 cases reported in 2024.

In 2023, there were 210 reported cases.

Environmental health executive director Dr Michael Lindsay said the department is encouraging the two-week buffer period because crypto is so easily spread through water.

“Waterborne transmission can happen when people accidentally swallow contaminated water while swimming in pools or other aquatic facilities,” Dr Lindsay said.

“People may not realise they remain infectious for some time after diarrhoeal symptoms stop, so that’s why we’re asking people to avoid swimming for two weeks after their symptoms cease.”

The parasite can survive for a long time in water and the environment and is not destroyed by regular chlorination, the department said.

“Currently, there is no evidence that any public swimming pools have faulty disinfection systems or are constantly infected. The Department is keeping a close eye on the situation,” it said.

It comes six weeks after The West Australian first reported the soaring number of case notifications to health authorities, with WA Health attributing about 20 per cent of WA cases to returned travellers from Indonesia in January.

It can take up to 12 days after exposure for symptoms to manifest, and people can be infectious from the onset of symptoms until two weeks after symptoms resolve.

There is no specific treatment for the infection and symptoms can last a few weeks in some people.

“The Department’s key priority is the prevention of further cases through alerting people about hygiene measures at pools and precautions to reduce the risk of spread in childcare facilities and household settings,” Dr Lindsay said.

Certain groups are more at risk of severe illness if infected, including younger children, pregnant women and people with weakened immune systems. Anyone concerned about their symptoms should contact their GP.

There were a staggering 14,018 cases recorded across the country in 2024, per the National Notifiable Disease Surveillance System, a more than 300 per cent increase on the 3718 cases nationally in 2023.