Health Department confirms Bali link to soaring rates of parasitic stomach bug in Western Australia

An outbreak of a gastro bug caused by a tiny parasite has been linked to overseas travel, with the majority of infected travellers returning to Western Australia from Indonesia.

WA Health Department data revealed 20 per cent of WA cases of cryptosporidiosis, a notifiable disease which can last for two weeks and causes nausea, stomach pain, diarrhoea and loss of appetite, were acquired from overseas.

Dr Paul Effler, the acting director of the Communicable Disease Control Directorate at the Department of Health, said Indonesia was “the most commonly reported country of travel”.

“Cryptosporidiosis is really common overseas and you can get it from food and water when you travel. Those individuals when they return can transmit to others in their household or other settings,” he said.

As reported in The West Australian on Wednesday, cryptosporidiosum infections increased 300 per cent to 800 between 2023 and 2024. So far this year 74 cases, almost three a day, have been reported to the WA Health Department.

Dr Effler said today almost half the notifications were in children.

“The 30 to 39-year-old age group were also commonly affected, possibly acquiring the infection from their children,” he said.

The actual number of cases in the community would be far higher than the data suggested, Dr Effler said.

“Many people will be asymptomatic and they’ll never get tested, and then there will be people with such mild illness that they won’t get tested either,” he said.

“So it is true that there are more cases out there than we actually count, but that’s also a good thing because it reflects the mild nature of the illness in general, that people don’t need to go get tested.”

Dr Effler said the increase in cases in WA could be in response to the community returning to pre-pandemic levels of recreation, such as using swimming pools.

He said because the bug is resistant to chlorine, it was important pool owners and managers maintained their filtration systems, and urged parents to keep children away from public pools for two weeks after diarrhoea symptoms resolved.

But he said the benefits of using swimming pools outweighed the risk of infection, which was low.

The Health Department also advised members of the community to take preventative measures to stop the spread of infection including washing hands, supervising children to make sure they wash their hands properly, washing and peeling raw vegetables and fruit, avoiding disinfected water and avoiding unnecessary touching of farm animals, especially young calves and lambs.

According to the National Notifiable Disease Surveillance System, a staggering 14,001 cases were recorded across the country in 2024, a 276 per cent increase from the 3717 national notifications in 2023.

Nationally, 46 per cent of cases occurred in children under the age of nine.

The Victorian Health Department this week urged members of the public to be cautious about using public swimming pools after 87 cases were recorded in the State over the past four weeks.

Victoria’s chief health officer Tarun Weeramanthri said patients could remain infectious for weeks after symptoms subside.