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Director General Of Health Privileged Statement

31 January 2000


THE public should avoid eating uncooked or lightly cooked Pacific oysters harvested between November 25, 1999 and January 4, 2000 from Northland's Waikare inlet, the Director General of Health says.

Dr Karen Poutasi said oysters from the inlet have been linked to recent outbreaks of food-borne illness caused by a Norwalk-like virus. About 150 people have reported being ill from this virus.

The Ministry of Health is talking to harvestors and processors to further identify the distribution of the affected oysters. Consumers should check the source of their oysters with their retailer. Processing companies are now withholding product harvested from the Waikare inlet during the affected dates.

The virus can occur in shellfish due to human faecal contamination, usually of the shellfish growing area.

"If you are unable to find out where your oysters were harvested, either cook them thoroughly until the centre is piping hot, feed them to your pets or throw them away. Freezing does not kill the virus. The virus will not harm pets," Dr Poutasi said.

Symptoms of the illness include nausea, vomiting, diarrhoea, abdominal pain, and headaches. Symptoms usually last for one or two days and while it was highly unlikely, the virus could cause serious disease. The virus spread easily and people with symptoms should practise good hygiene and avoid preparing food for others for seven days following the onset of the illness, Dr Poutasi said.

"People who have severe symptoms, or symptoms for longer than two days should seek medical advice."

Public health services are investigating the outbreaks and further inquiring into the source of the contamination.

The following companies harvested, processed or distributed oysters sourced from Waikare Inlet between 25 November 1999 and 4 January 2000.

HARVESTERS: Tindall Oysters Limited, Ika Marine Limited. PROCESSORS/DISTRIBUTORS: Seafood Harbour (1997) Ltd, Kia Ora Seafoods, Roff Seafoods, Peters Best Oysters Limited, Pacific Marine Farms (1996) Ltd, The Oysterman, Crean Foodservice Limited, Oceanic Foods Limited, F.E. Lockey and Company.

Further updates will be given to the media and posted to the Ministry's website as additional information becomes available.


For further information contact; Sue McCabe, Media Advisor, 04 496 2067 or 025 495 989 Internet Address;

Questions and answers on Norwalk-like viruses

What are Norwalk like viruses?

A group of viruses that cause disease in humans and are a common cause of food poisoning outbreaks. They survive freezing, but are killed by heating to 90 C. Eating raw shellfish is a common cause of outbreaks both in New Zealand and internationally. The virus can be transmitted by contamination of food and water, and from person to person. Filter feeding shellfish are easily contaminated by faecal (sewerage) contamination of the water where they are grown.

How do you know oysters from the Waikare inlet have caused this illness?

Recent outbreaks of vomiting and diarrhoea have been traced to people eating raw Pacific oysters harvested from the Waikare inlet in Northland. Auckland Healthcare Services investigated 64 cases of people being ill in December, while Health Waikato investigated 13 cases of illness in January. Those tested for a Norwalk-like virus had positive results. The ill people were more likely to have consumed oysters than those in their company who did not become ill. Samples of oysters harvested from the Waikare inlet in Northland have also tested positive for the virus.

What happens to people who eat infected oysters?

Norwalk like viruses cause a short unpleasant illness characterised by nausea, vomiting, and diarrhoea 24 to 28 hours after eating the contaminated food. The illness usually lasts for one or two days and there is no specific treatment for the illness. However, people who have severe symptoms, or an illness lasting beyond two days should contact their doctor for advice. People with the symptoms can infect others and should avoid food preparation for seven days after the onset of symptoms.

How can customers identify where their Oysters came from?

The alert does not apply to Bluff oysters, oysters harvested in locations other than the Waikare inlet, and to oysters harvested in the Waikare inlet before the 25th November 1999 and after the 4th of January 2000. Labelling on your oysters may help identify their origin and the retailer who sold the oysters may have more information. The Ministry of Health has provided information on some of the distributors of the implicated oysters and this information will be updated on the Ministry of Health website. Further updates will be given to media and posted to the website as necessary.

What should people do if they cannot find out where their oysters came from?

To avoid the risk of illness people should thoroughly cook any frozen or fresh oysters until they are piping hot, feed them to their pet or throw them away. The virus does not affect animals.

What has led up to the Ministry's issuing of the warning?

The Ministry acted as soon as it became aware outbreaks of food poisoning had been reported. The action the Ministry took includes ensuring the shellfish industry have acted to isolate affected product, reviewing the information gathered from investigations and liaising with the Ministry of Agriculture to ensure the shellfish sold in New Zealand is managed the same way as the exported oysters The Ministry has to protect the public's health but is also aware of the alarming effect warnings have and the implications this can have on an industry.

There was an inevitable delay between when the oysters were harvested, processed, distributed, consumed, the onset of illness and then the investigation into the illness and its findings.

MAF have taken action on oysters that have been exported. For further information on MAF's actions contact them.

Why was November 25, 1999 the start date for the warning period?

The warning period is based on evidence obtained from investigations. The Ministry is not aware of any potential contamination prior to that date.

What proportion of the oysters on the market are affected?

The majority of fresh oysters sold in recent days would have been harvested after the period the warning applies to. The product the Ministry is most concerned about is oysters that have been frozen, either by the distributors, restaurants, other retailers, or consumers. the Waikare inlet is one of 11 growing areas in the Northland region and it is estimated to supply 20 per cent of the New Zealand oyster market.

How do we know that the Waikare inlet is free of contamination now?

This is based on evidence from investigations conducted by Northland Health and Auckland Healthcare Services. There are no new outbreaks of illness under investigation. The closure period would be reviewed if further outbreaks implicating Waikare inlet oysters were reported.

What are you going to do to ensure this does not happen again?

The Ministry will undertake a review of the incident. The review will help establish how to best avoid Norwalk-like virus contamination, how to detect it quickly and how to manage it.


Please attribute the Question and Answer information to Ministry Advisor, Dr Douglas Lush

For further information contact; Sue McCabe, Media Advisor, 04 496 2067 or 025 495 989 Internet Address;

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