• The number of cryptosporidiosis cases in the wider Wellington area this year has risen to at least 59.
• The outbreak, which was earlier said to be linked to public swimming pools, is now spreading through households, schools, and early childhood centres, with more cases expected.
• A Lower Hutt swimming pool has now been closed and drained because a symptomatic person attended a swimming lesson.

Another public pool has had to be drained after a person sick with a highly contagious parasitic stomach bug circulating in the Wellington region attended a swimming lesson there.

Cryptosporidiosis – which one woman said was so bad she nearly called an ambulance – started spreading in the Hutt Valley a few weeks ago with links to public swimming pools, and has now leaped to Wellington, Porirua, Kāpiti and Wairarapa.

Hutt City Council today announced its hydro pool at Huia Pool is closed so it can be drained and cleaned as a precaution.

“The decision came after Public Health advised council someone attended swimming lessons on Saturday 5 April while they were symptomatic. That person contracted the crypto bug from a different source – not any of our pools," the council’s statement said.

The council has not said whether the person was an adult or child.

“Public Health were happy for us to make our own decision on whether we did any extra treatment at the Huia Hydro Pool. We have decided, in the interest of everyone’s safety, to close, drain and give the pool a deep clean.”

Swim classes for today have been cancelled, potentially through to Saturday.

Cryptosporidiosis is a disease caused by a microscopic germ (parasite) called Cryptosporidium. Image / CDC

“Meanwhile, Public Health advised us at the end of last week that three cases of cryptosporidiosis had been linked to Te Ngaengae Pool. However, their attendance at the pool pre-dated our initial draining and intensive treatment of the pools. Public Health are satisfied we have dealt with the situation.

“We would like to stress the importance of taking a shower before entering swimming pools, and not to swim within a two-week period after they have had any symptoms of diarrhoea or vomiting. This will ensure the health of all pool users.”

As of Saturday morning, central region medical officer of health Stephen Palmer said there had been 59 confirmed cases of the bug in the Greater Wellington region since the start of the year.

“The majority of cases are from the Hutt Valley area,” Palmer said in a statement.

Of the total cases, 37 resulted from people who used a pool or had contact with an ill household member who used a pool.

“It is likely that there are more cases in the community because not everyone reports being unwell with crypto,” Palmer said.

In 2023, which is the last year ESR has data for, there were 31 cases of the illness in the Capital and Coast and Hutt Valley DHB areas. In 2022 there were 42.

“Health NZ has alerted all pools to the current increase in gastro illness. When there is increased crypto illness in our communities, it is recommended that all pools take additional action to reduce the likelihood of the crypto bug circulating in their pool system,” Palmer said.

“We have also issued advice to early childhood centres across the Greater Wellington region as crypto can spread easily, especially among younger children.

“Crypto is a gastro bug that causes vomiting and diarrhoea and people can remain infectious for up to two weeks, which is why good hygiene and cleaning practices are important. People who have been unwell must not swim for two weeks after diarrhoea has stopped – crypto can still spread for two weeks after the illness has gone away."

Washing with soap and water is recommended over using hand sanitiser, which does not kill the parasite. Photo / Hafiez Razali

Health officials earlier confirmed cryptosporidiosis cases were connected to the toddler pool at Te Ngaengae and the hydrotherapy pool at Huia.

In response, Hutt City Council closed and disinfected both pools using high doses of chlorine and ultraviolet light, in accordance with public health guidelines.

“As soon as we were made aware, we took immediate action,” read a statement at the time from Hutt City Pools + Fitness.

“Both pools were closed and underwent an intensive treatment process ... There is no indication there had been further cases from the complex.”

As a further precaution, several pools were drained and refilled.

“We have decided to close the shallow leisure and deep leisure pools at Te Ngaengae ... and the Huia hydrotherapy pool so they can be fully drained and refilled with fresh water.”

Health recommendations include:

• Soap and water instead of hand sanitiser, which does not kill the parasite.
• Close monitoring of tamariki hand washing, especially after illness.
• Cleaning with hot, soapy water before applying disinfectants like bleach, as crypto is resistant to many cleaners.
• Strict pool hygiene rules, including ensuring children shower and use the toilet before swimming and avoiding pools for two weeks post-illness.

The parasite cryptosporidium can cause vomiting, cramping and diarrhoea and is not easily detected in regular pool-water testing.

Fact sheets and swimming guidelines are available through the Health New Zealand Te Whatu Ora website.

Melissa Nightingale is a Wellington-based reporter who covers crime, justice, and news in the capital. She joined the Herald in 2016 and has worked as a journalist for 10 years.