At least 53 people contracted norovirus in late August and early September, including 15 to 20 Australian tourists.
Public Health South tests found norovirus in the township's water supply and Otago Regional Council director of resource management Dr Selva Selvarajah told the Otago Daily Times this week staff were investigating two sewage disposal systems - one from the Cardrona Hotel and the other from the Braemar Resort.
However, he believed it might not be possible to establish exactly where the source of the problem lay.
Cardrona has three privately owned wastewater treatment plants and a number of septic tank systems.
Dr Selvarajah said the township needed to quickly find a long-term solution to its sewage-disposal problems to ensure the water supply was safe and also to safeguard the region's reputation in the tourism market.
The Queenstown Lakes District council has been considering a new community wastewater scheme for Cardrona township (permanent population 60) for more than five years and is consulting residents about how a scheme might operate.
The options considered all involve discharging treated wastewater on to land.
However, discharging to land would have to meet very high standards, including "stringent" nitrogen requirements, Dr Selvarajah said.
He suggested the option that might best suit the Cardrona Valley was to pipe effluent the 25km to Wanaka for treatment and disposal there.
While he acknowledged this would be expensive, it would provide the three skifields in the Cardrona Valley, and existing and proposed developments, with the opportunity to work together to solve their effluent disposal issues, he said.
"It makes sense to manage the issue in a co-ordinated fashion."
Medical officer of health Dr Derek Bell told the ODT this week Public Health South would have "a big interest" in seeing the problem resolved.
Dr Bell said the "take-home" message from the norovirus outbreak was that when there was environmental contamination then "we have waited too long and we need to address things urgently".
Cardrona Ski Resort marketing manager Nadia Ellis said the skifield was not implicated in the norovirus outbreak and she was not aware of any feedback from customers.
"Nothing suggests to me a lot of people in Australia have been talking about it or that it's affected our reputation," she said.
