'Extreme' norovirus risk from Estuary shellfish

Seafood enthusiasts have been warned to stop gathering shellfish after "extremely high levels of norovirus" have been found in Christchurch.

A health warning has been issued by the Canterbury District Health Board after contaminated shellfish were found around the mouths of the Avon and Heathcote rivers, and at other locations around the Avon-Heathcote Estuary.

Canterbury Medical Officer of Health Dr Alistair Humphrey said people should not collect or eat shellfish from anywhere in the estuary, including along the causeway, until further notice.

Norovirus is found in the faeces and vomit of infected people and Humphrey said individuals could be infected through direct contact with a sick person, by eating contaminated food or water, or by touching surfaces and objects contaminated with the virus.

"Recent tests have confirmed that shellfish have become contaminated with very high levels of norovirus," he said. 

"This is because of the ongoing direct discharge of sewage into the Avon and Heathcote rivers, as well as the direct discharge into the Estuary as a result of the February and June earthquakes."

Signs had been placed in infected areas and Humphrey said ignoring the warnings could have life-threatening consequences.

Symptoms often begin suddenly and include vomiting, diarrhoea and stomachaches. People may also have a fever, chills, headache and muscle aches. The illness is usually brief, but symptoms could persist for several days and become life-threatening.  

"We would also like to remind people that contact with river and sea water in and around Christchurch City should be avoided. 

The only areas where water quality has been found to be acceptable are Pegasus Bay beaches north of the Waimakariri River, the lower Waimakariri River, Spencerville Beach and Taylors Mistake south including Lyttelton Harbour," Humphrey said.

However, contact with water in these areas should be avoided following heavy rainfall for up to 48 hours.

The contaminated sites would continue to be monitored and the public would be informed when it was safe to gather shellfish again, he said.