Food poisoning

Most food poisoning is caused by harmful bugs (pathogens) getting into food.

The most common types of food poisoning are:

1. bacterial eg Salmonella, Campylobacter, E.coli and Listeria
2. viral eg Norovirus, Rotavirus and Hepatitis A
3. intoxication caused by the toxins produced by some bugs such as Staphylococcus aureus, Bacillus cereus and Clostridium perfringens.

Some of these bugs can also be transferred from person-to-person with or without symptoms, or via contaminated surfaces. The symptoms they cause are the same even if food is not involved.

Some people have allergies and intolerances to specific foods or ingredients. These are not considered food poisoning, although they can also be very serious and even life threatening. See allergies and intolerances.

Symptoms of food poisoning range from mild to very severe.

Symptoms usually take between a few hours to a few days to begin and may last for a few days, depending on the type of pathogen.

Symptoms often include one or more of:

• nausea
• stomach cramps
• diarrhoea
• vomiting
• fever
• headaches

Some foods accommodate harmful bugs or toxins more than others.

The bugs or toxins may be present on foods at the time of purchase, get onto food by cross contamination and poor hygiene, or grow to harmful levels as a result of poor temperature control.

Harmful bugs can be:

• carried on the bodies of people handling food
• frequently present in the throat, nose, skin, hair and faeces
• transferred to food after touching the nose, mouth or hair or smoking without washing hands before handling food. Sneezing or coughing around or near food can also lead to contamination.

Food poisoning can be caused by:

• not cooking food thoroughly
• not storing food that needs to be chilled below 5°C
• someone who is ill or has poor hand hygiene handling the food
• eating food after a ‘use-by’ date
• cross contamination, where bacteria is spread between food, surfaces, utensils and equipment

Higher risk foods include:

• meat, especially undercooked mince and rolled, formed or tenderised meats
• raw or undercooked poultry such as chicken, duck and turkey
• raw or lightly cooked eggs including foods made from raw egg such as unpasteurised mayonnaise
• smallgoods such as salami and hams
• seafood
• cooked rice not kept at correct temperatures
• cooked pasta not kept at correct temperatures
• prepared salads such as coleslaw, pasta salads and rice salads
• prepared fruit salads
• unpasteurised dairy products

Diagnosing correctly that illness is caused by food poisoning and identifying the particular cause can be difficult. Identifying the cause is not always possible.

For details on common food poisoning bugs (pathogens), onset of symptoms after eating and typical foods, see foodborne illness pathogens

Some people can be more vulnerable to, or are affected more by the symptoms of food poisoning.

These include:

• pregnant women
• people older than 65 years of age with certain underlying conditions, and
• people with compromised immune systems through chronic or acute ill health and some conditions and treatments

In rare cases, food poisoning can result in long-term health problems and even death.

See: life events

People with diarrhoea and vomiting from any cause should stay home from work or school and drink plenty of fluids.

Where possible, people should avoid preparing food at home while ill and for 2 days after their symptoms have finished. They may still spread some illnesses via food for this period after symptoms have stopped.

See also: Viral Gastroenteritis (Ministry of Health)

The risk of food poisoning can be minimised, by following these key tips.

Is it food poisoning?

Was it the last thing you ate?

Is the cause to be found in what you bring up?

See: fact or fiction

Most cases of food poisoning do not require medical attention. But contact a doctor if:

• symptoms persists for more than 3 days or are very severe
• not able to keep fluids down for more than a day
• symptoms include blood or mucus in the vomit or diarrhoea
• the person is at risk of dehydration such as infants and the elderly. Consult their doctor as early as possible

Further questions about illness possibly caused by food? Consult a doctor or call the local Public Health Unit.

If you believe you are experiencing food poisoning caused by food that was purchased, you can report it in case an investigation is warranted.

See: food complaints

The health and illness-related information on this page is offered for general information and educational purposes only.

It is not medical advice.

For further explanation of this note, please see the full disclaimer.