An acute norovirus outbreak in the Cardrona township of New Zealand during last year’s ski season was caused by sewage contamination of drinking water and the wider environment, a peer-reviewed investigation says.
The month-long outbreak of norovirus that caused at least 53 cases of diarrhoea, vomiting and nausea was only the third documented waterborne transmission in New Zealand.
Crucially, the report also says a strategy is “urgently required” to decrease environmental contamination of drinking water supplies, improve sewage disposal and manage drinking water.
The report, in the New Zealand Medical Association journal by Dr Derek Bell, Susan Jack and Joanne Hewitt, discusses the investigation of the waterborne gastroenteritis outbreak that infected at least 53 people in and around Cardrona in mid-August and early September last year.
The Southern District Health Board yesterday confirmed the article, which mentions a hotel and resort in “southern New Zealand”, referenced the Cardrona township, the hotel and accommodation providers in the village.
Cardrona Hotel, under new management earlier this year, has a supply from a bore and the hotel water system supplies water to neighbouring properties via 11 water access points. Another township accommodation provider, Benbrae, has an independent water supply and sewage system.
Public Health South investigated, interviewing 66 people, collecting samples, visiting the site, inspecting premises and water supplies.
The illness lasted, on average, for 36 hours and the cases included 12 Cardrona residents.
Hotel drinking water samples and the hotel bore were positive for norovirus, a drinking tap from the neighbouring accommodation was positive, and river samples and water downstream of the wastewater disposal field were positive.
A supply runs from a 14-metre deep bore, the water is chlorinated and pumped to holding tanks, then gravity-fed to the hotel and other access points. There was inadequate chlorination, an ineffective chlorine pump and there was surface flooding contamination, the article says.