Authorities in New Zealand are looking into three recent Listeria cases to see if they are linked and to find a source of the infections.

While investigations are underway to find the vehicle of infection for the reported cases in Tauranga, a city in the Bay of Plenty region, officials cautioned that often a source cannot be identified for individual cases.

The three cases, aged in their late 70s to 90s, were notified to Toi Te Ora Public Health between July 12 and 20. All three were hospitalized and one person with a previously diagnosed terminal condition has died.

Toi Te Ora Public Health and the Ministry for Primary Industries (MPI) reminded the public of recommended food safety measures to reduce risk from Listeria.

“Our investigations include determining what the cases may have eaten in order to identify any common risk factors or food that may be the source of infection,” said Dr. Neil de Wet, medical officer of health for Toi Te Ora Public Health.

Warning to vulnerable groups
MPI compliance director Gary Orr said that if there was a link identified between cases and the food supply chain, immediate action would be taken to ensure public safety.

People at risk of more serious illness from Listeria include pregnant women and their unborn babies, newborn babies, those with weakened immune systems and elderly people, especially if they have poor health. The Bay of Plenty typically sees one to five cases each year.

MPI advised people in an at-risk group to avoid 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 and chilled pre-cooked meats including chicken, salami and other fermented or dried sausages; pre-prepared, pre-packed or stored salads including fruit salads and coleslaws; raw milk and any food containing unpasteurized milk; soft-serve ice creams and soft, semi-soft or surface-ripened soft cheese such as brie, camembert, feta, ricotta or Roquefort.

Listeriosis is an infectious disease caused by the bacterium Listeria monocytogenes. Symptoms include fever, muscle pain, septicemia (blood poisoning) and meningitis. The incubation period is usually one to two weeks but can vary between a few and 70 days.

Botulism linked to sea snails
The Bay of Plenty was also involved in an outbreak of botulism in May, according to a monthly surveillance report. ESR manages the national reportable disease database (EpiSurv) on behalf of the Ministry of Health.

Four people who ate home-preserved sea snails were admitted to a hospital. Botulism was confirmed in clinical samples and the leftover home-preserved shellfish.

Botulism is a rare but life-threatening condition caused by toxins produced by Clostridium botulinum bacteria. In foodborne botulism, symptoms generally begin 18 to 36 hours after eating a contaminated food. However, they can start as soon as six hours after or up to 10 days later.

It can cause symptoms including general weakness, dizziness, double-vision, and trouble with speaking or swallowing. Difficulty in breathing, weakness of other muscles, abdominal distension and constipation may also occur. People experiencing these problems should seek immediate medical attention.