Vibrio bacteria

Vibrio bacteria can make you sick

The main type of Vibrio bacteria of concern is Vibrio parahaemolyticus.

Symptoms of Vibrio parahaemolyticus infection

• Symptoms usually appear within 4 hours but normally between 12 and 24 hours after eating contaminated food.
• You may suffer abdominal cramps, watery diarrhoea, nausea, vomiting, and fever.
• Illness lasts between 1 and 7 days. In most cases medical treatment is not needed but in severe cases, you might have to go to hospital.
• Occasionally, septicaemia (blood poisoning) can occur.

Raw or undercooked shellfish may contain Vibrio bacteria

Foodborne Vibrio infection can occur:

• by eating raw or undercooked shellfish
• because of cross contamination between raw shellfish and cooked food.

Vibrio is present in greater levels in warmer seawaters over 15°C. That is why, in general, more illnesses occur over the summer months. They also multiply rapidly if shellfish is held at warm temperatures after harvest, so it's important to store and refrigerate these properly to minimise its growth.

Vibrio parahaemolyticus infection is widespread and has been recorded in all parts of New Zealand. Shellfish containing Vibrio parahaemolyticus does not smell, taste, or appear "off".

How to lower your risk of getting sick from Vibrio

Lower your risk of getting sick by following recommended food handling tips.

Those with low immunity, such as young, old, pregnant and immunocompromised, are at particular risk and should avoid raw or undercooked fish and shellfish.

Gathering and transporting tips

• When gathering shellfish, keep them alive and cool to keep them fresh.
• Keep them in a bucket of fresh seawater out of the sun to let them de-sand.
• Use a chilly bin to store and transport them home. Put ice wrapped in a towel in the chilly bin to protect the shellfish from getting too cold and killing them.

Storing at home tips

• Refrigerate shellfish as soon as possible. Store in a bowl covered with a cold, wet towel, on the bottom shelf, below cooked food.
• To freeze shellfish, shell them as soon as possible and freeze in small amounts in their cooking water or natural juices.
• Thaw frozen shellfish before cooking, in the fridge.

Preparing and cooking tips

• Use shellfish within 2 days of harvest. Don't eat or cook ones that have died or have broken shells.
• Keep hands, chopping boards, knives, and utensils clean to prepare raw shellfish.
• Keep raw shellfish separated from other cooked products or ready-to-eat products.
• Don't eat shellfish raw or undercooked. Cook thoroughly until they are at least 65°C for 1 minute (until they open and are firm to touch).

How to avoid cross-contamination

Vibrio can spread to different food and surfaces either from the shellfish itself, its liquid or juices, your hands, or cooking equipment. This is called cross-contamination and it increases the risk of getting sick.

To help avoid cross-contamination:

• use different chopping boards, plates and bowls, and knives for raw and cooked shellfish
• wash your hands.

Also, prevent raw shellfish contaminating other ready-to-eat foods, for example cooked foods and salads.

Learn more about cross-contamination and how to avoid it

Posters for retailers of shellfish

If you are a retailer of shellfish, you need to download a copy of the below Point of sale notice and display it in your store.

Poster for retailers – Important advice to thoroughly cook shellfish [PDF, 203 KB]

Cook shellfish thoroughly poster [PDF, 106 KB]

Find out more

Food safety when fishing and gathering shellfish

Food safety for people with low immunity

Food safety for pregnant women

Food safety when you're sick

Who to contact

If you have questions about Vibrio, email info@mpi.govt.nz