Public health authorities are investigating the cause of a norovirus outbreak in an Otago township which affected 66 people in 15 days.
The infection in Cardrona occured between mid-August and early September.
Medical officials say tests have shown wastewater systems in the area are likely to have been the source of the outbreak.
Medical Officer of Health Derek Bell says it is thought the infection was spread through person-to-person contact, though some may have been waterborne.
Dr Bell says a policy to boil water has stopped further cases of the virus.
Public health authorities will be working with the community and Queenstown Lakes District and Otago Regional Councils to make improvements to the wastewater and drinking water schemes.