By Rowan Quinn for RNZ

One person has died and two people have been hospitalised with listeria in Tauranga, prompting a warning to pregnant women and others at risk.

Authorities are urgently trying to find the source of the dangerous bacteria which can be found in raw fish, processed meat, hummus and many other cold foods.

It is dangerous for newborn or unborn babies, elderly people, or those with poor immunity.

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The region's medical officer of health, Neil de Wet, said all three of those who were affected were between 70 and 90 years old.

The person who died already had a terminal condition, he said.

It was possible the cases were linked because it was unusual to see three in two weeks, Dr de Wet said.

Usually the region had between one and five cases a year.

An investigation with the Ministry for Primary Industries was under way to find the source.

Its compliance director Gary Orr said they will look to see if there is a common food connection.

Authorities are urgently trying to find the source of the dangerous bacteria.
Authorities are urgently trying to find the source of the dangerous bacteria.

"Any case of listeria is a worry for us, particularly if there is a link to food ... If it is shown to have a link to food then we will move very quickly to take that risk food out of the system or alert the public," he said.

Public health officers would interview the patients or their families about where they had been and what they had eaten to see if there was a link.

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Pregnant women and other groups vulnerable to the disease should follow the usual advice to avoid risky foods, Dr de Wet said.

Food safety

While detailed investigations are underway and a source of infection for these recently notified cases is not yet clear, and often a source is not able to be identified for individual cases, it is a timely reminder that people who are in an at-risk group should avoid certain foods.

These foods include:
• uncooked, smoked or ready-to-eat fish or seafood, including oysters, prawns, sashimi or sushi.
• paté, hummus and tahini-based dips and spreads.
• cold pre-cooked chicken.
• processed meats including ham and all other chilled pre-cooked meat products including chicken, salami and other fermented or dried sausages.
• pre-prepared, pre-packaged or stored salads (including fruit salads) and coleslaw
raw (unpasteurised) milk and any food that contains unpasteurised milk.
• soft-serve ice creams.
• soft, semi-soft or surface-ripened soft cheese (for example, brie, camembert, feta, ricotta, roquefort).

If you or anyone in your household is in an at-risk group, it is especially important to take a few simple food safety precautions:
• Avoid eating the high-risk foods listed above.
• Follow good food hygiene practices, such as washing and drying hands before preparing food and after handling or preparing raw foods.
• Eat freshly cooked or freshly prepared foods.
• Wash all raw fruit and vegetables very well before eating.
• Cook foods thoroughly.
• Refrigerate leftovers immediately and do not keep for more than 2 days. Reheat to steaming hot before eating.