Selwyn gastro outbreak being investigated

Thursday August 23, 2012

‚ÄčThe Canterbury District Health Board is investigating whether an outbreak of gastroenteritis at Darfield and Hororata was from contaminated water supplies.

The investigations follow 19 confirmed or suspected gastroenteritis cases in the region, one of which has resulted in hospitalisation.

Dr Alistair Humphrey, Canterbury Medical Officer of Health says many more are expected to have had symptoms as not all those suffering from gastroenteritis will have visited their General Practice Team.

"While Selwyn District Council testing has shown the water in Darfield and the Selwyn Rural Water Supply's Hororata branch is now safe to drink, it is possible that the gastroenteritis outbreak was caused by problems with water supplies late last week," Dr Humphrey says.

"The notifications coincide with water supply issues the region has been experiencing.  In June the council reverted to its river supply because of problems with its deep bore system. The heavy rainfall over the last few weeks has put additional pressure on water supplies."

The CDHB is carrying out both clinical and public health investigations to determine the source of the outbreak, he says.

"New Zealand's drinking water standards ensure there are several barriers between potential infection and water related illness. Infection usually occurs when more than one of these barriers breaks down, and there is rarely a single cause.

"CDHB's Community and Public Health team is working closely with the Selwyn District Council so its community can be confident of the quality of their drinking water."

Dr Humphrey says water storage tanks on residential properties may still contain contaminated water.

"The safest approach for getting rid of potential contamination in storage tanks is to drain them; alternatively residents with very large tanks can use bleach to remove potential contamination as described in the guidelines on the Selwyn District Council website."

The guidelines can be found at:

Page last reviewed: 24 July 2013