A week after a boil water notice was put in place in parts of Queenstown, the Queenstown Lakes District Council and Te Whatu Ora Health New Zealand (HNZ) are no closer to working out the source of the outbreak.
While it was initially thought to be in the district’s water supply, the authorities are now focusing on sources of infection other than widespread contamination of the water.
While the investigation continues, the boil water notice issued by the council for Queenstown and Frankton residents and businesses on a public supply remains in place.
Lakes District Hospital has clean water and a water tanker has been brought in to continue to supply clean water.
At 9am yesterday there were 30 confirmed cases, another nine probable cases and seven under investigation.
Most cases confirmed were aged between 15 and 39, with one case under 10.
One person received treatment in hospital due to complications from crypto, but has since been discharged.
HNZ incident controller Lynette Finnie said a "heat map" of positive cases’ places of residence and work showed most were from the CBD area.
A joint agency incident management team had been working on the response since September 19.
Southern health protection officers, with support from across the South Island, had been interviewing positive cases to determine any links between them, or potential common contamination sources.
Medical officer of health Dr Emma Sherwood said determining the source of infection was complex and difficult because it could be spread in so many different ways.
"The standard potential sources of contamination include from people who have recently travelled overseas, food or drink products, hospitality premises, recreational water, or water that’s been tainted by parasites from animals — that’s a huge pool of potential sources of infection."
Officers had also been investigating practices at hospitality businesses and those producing food and using water in manufacturing processes.
"We are not confining the source investigation to just the local water supply."
Ms Finnie said the investigation team was leaving "no stone unturned".
"We want to get to the bottom of this as quickly as possible.
"We acknowledge this is a massive inconvenience to the public, businesses and the hospitality and tourism industries."
On Saturday night, Queenstown Lakes District Mayor Glyn Lewers said the council hoped to get the boil water notice removed at Kelvin Heights and was "working very hard" to get a protozoa barrier in place at the Two Mile intake.
He expected to have an update on a timeframe for installing an ultraviolet water filter — being sent down from the Waimakariri District Council — by the end of this week.
When asked if the QLDC had bought the UV filter, or if it was on loan, Mr Lewers responded:
"There are some commercial sensitivities there. We’re trying to get the best price for the ratepayer so we’ll just leave it with that."
In Queenstown on Saturday, Emergency Management Minister Kieran McAnulty said it was important for the authorities to identify the source of the parasite.
"We’re working alongside the council and the authorities to help them where we can and once we know the guts of it we can start talking about what support can be provided.
"I came down here to offer support, identify where we can help in the immediate instance and also spread the message that Queenstown is open for business."
The most common symptom of Cryptosporidium infection is smelly, watery diarrhoea and stomach cramps.
People who live, work or have visited Queenstown and Frankton on or after August 18 and have symptoms should inform their GP or health provider and arrange testing if needed.
Do not show up with a sample without having first talked with your healthcare provider.
Health authorities said the best way to stop the spread of Cryptosporidium infection was to practise good hand hygiene.
This meant washing hands with soap and water for at least 20 seconds and drying them thoroughly with a clean towel.
Hand sanitiser was not effective for countering crypto.
Residents were also urged to avoid contact with flood waters and assume it was contaminated by sewage.
All items that had come into contact with flood waters should be treated with caution.
For those cleaning up, protective clothing, gloves, sturdy footwear and face masks should be worn.