Queenstown's council has secured UV disinfection equipment to provide a temporary barrier against a gastro bug that has hit the popular tourist town, but it will not be in place until December.
There are now 48 confirmed cases of Cryptosporidium (up from 45), 12 probable cases and three are being investigated.
Three people have been admitted to hospital as the disease is transferred from person to person, and since discharged.
Te Whatu Ora Health New Zealand (HNZ) said drinking water had not been ruled out as the source of the outbreak.
In a statement yesterday, the Queenstown Lakes District Council said its current timeframe for installing the temporary treatment at the Two Mile water supply plant was by December 8.
Mayor Glyn Lewers said a plan was now in place and this would provide more clarity about what the solution looked like and when a boil water notice might be lifted.
Property and infrastructure general manager Tony Avery said the first step was to install the UV treatment at Two Mile, but due to a lack of availability of ideally sized equipment the first intervention would be a temporary solution to address the immediate need and respond to a compliance order.
"This temporary solution will do what we need in the short term but larger UV reactors, which have also now been ordered, are required long term," Mr Avery said.
"Once the larger equipment arrives, we will swap out the temporary systems for use elsewhere in the district.
"This approach, and taking this opportunity to secure other units, means that we are able to promptly implement UV treatment not only at Two Mile but also water supplies at Western Wānaka, Beacon Point in Wānaka and Luggate."
The council estimated the temporary UV treatment would take ten weeks to implement.
"That ten-week programme included undertaking detailed design, procurement of the component parts and fabrication of the container housing for the equipment, delivery, site connection and commissioning, and flushing of the network.
"Further details of the full programme, including the timeline for installing the larger UV reactors at Two Mile will be provided next week."
The council was trying to isolate the Kelvin Heights water supply network, which has an effective barrier against protozoa such as Cryptosporidium, from the Two Mile network.
It was working with water services regulator Taumata Arowai to try to lift the boil water notice before the end of the school holidays.
HNZ Southern medical officer of health Dr Emma Sherwood told RNZ confirmed cases were being re-interviewed to try to find a definitive link to drinking water or food.
Further testing of drinking water was under way.
Dr Sherwood said some people had been getting it from people they lived or worked with as a secondary infection, so it was important everyone practised good hand hygiene.
The council statement said it was exploring options with Taumata Arowai that might enable the boil water notice to be completely lifted earlier, as current testing of the water supply suggested there was no contamination issue.
Testing of the water supply in the affected area continued to return negative results for the presence of Cryptosporidium or other signs of contamination.
The extensive sampling and testing programme was ongoing, the council said.
Advice from Te Whatu Ora to minimise the risk of secondary infection was.—
Wash your hands with lots of soap and water for at least 20 seconds and then dry them thoroughly on a clean towel.
Do not rely on hand sanitiser, as this is not effective against Cryptosporidium.
If someone in your household has cryptosporidiosis, ensure all surfaces, including door handles, are cleaned regularly with a cleaning product that contains hydrogen peroxide.
Chlorine-based products do not work against Cryptosporidium and bleach-based products are not as effective. — Additional reporting RNZ
