Food poisoning

On this page

• 1. If you think you currently have food poisoning
• 2. How is it treated? What should I do? ... HELP!
• 3. What is foodborne illness or “food poisoning”?
• 4. Types of foodborne illness
• 5. How do bacteria get in food?
• 6. Who is at risk?
• 7. How to reduce the risk?
• 8. Exposing foodborne illness “myths”

1. If you think you currently have food poisoning

If you think you currently have food poisoning, see our "Help!" section.

Although it is widely accepted that Australia has one of the safest food supplies in the world, each year an estimated 5.4 million Australians suffer from foodborne illness.  Fortunately, fatalities are extremely rare, although anyone who has suffered food poisoning knows the symptoms can be extremely unpleasant.  Foodborne illness also has a significant economic impact on the individual and community in terms of medical costs and lost working hours.

2. How is it treated? What should I do? ... HELP!

1. Many people have mild symptoms and recover within a few days. However, if symptoms persist for more than 3 days or are very severe you should seek medical advice.
2. You should see a doctor immediately if your symptoms include blood or mucus in the diarrhoea.
3. People at risk of dehydration such as infants and the elderly should consult their local doctor as early as possible.
4. People with diarrhoea and vomiting should stay home from work or school and drink plenty of fluids.
5. As a precaution, they should not prepare food for 48 hours after their symptoms have finished.

Any health- and illness-related information above is offered for general information and educational purposes only. It is not medical advice. For further explanation of this note, please see our disclaimer.

See also factsheet Viral Gastroenteritis .

If you have further questions about illness which is possibly caused by food or other questions about your health, consult your doctor or call your local Public Health Unit.

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3. What is foodborne illness or “food poisoning”?

Foodborne illness generally results from consuming food or drink contaminated with pathogenic bacteria, viruses or toxins.  It often produces symptoms such as nausea, vomiting, stomach pain, diarrhoea, or fever. The symptoms are often the same as for gastro-type illnesses caused by other sources (other people carrying the bacteria, unhygienic surfaces, etc). This usually makes it hard to tell illness caused by food from the other sources of illness.

Bacteria causing illness in humans are called pathogens. They are found in many places, including in human and animal faeces.  When these potentially harmful pathogens enter the food supply they can cause foodborne illness. Foodborne illness can occur from any fresh or processed foods consumed in a range of settings such as homes, restaurants, large catering establishments, schools and institutions. Most cases of foodborne illness can be avoided through good hygiene and good food handling practices.

4. Types of foodborne illness

1. Bacterial eg Salmonella, Campylobacter, E.coli, Shigella and Listeria;
2. Viral eg Norovirus, Rotavirus and Hepatitis A;
3. Intoxication caused by toxins produced by pathogens such as Staphylococcus aureus, Bacillus cereus and Clostridium perfringens.

Symptoms will vary depending on the type of pathogen, and may include diarrhoea, vomiting, nausea, abdominal pain, and fever.  Other symptoms may include headache, jaundice, and numbness.  Symptoms can take between a few hours to a few days to develop and may last for a few days, depending on the type of pathogen.

Some common pathogens and their features:

Pathogen	Microscopic image of pathogen	Incubation period (time between eating and onset of symptoms)	Symptoms	Associated foods *
Bacillus cereus toxin (vomiting)		1 - 6 hours	Sudden onset of severe nausea and vomiting	Improperly refrigerated cooked rice
Bacillus cereus toxin (diarrhoea)		6 - 24 hours	Abdominal cramps, nausea and watery diarrhoea	Meats, stews, gravy, vanilla sauce
Campylobacter		2 - 5 days	Fever, nausea, abdominal cramps and diarrhoea (sometimes bloody)	Raw and undercooked poultry, unpasteurised milk and contaminated water
Clostridium perfringens toxin		6 - 24 hours	Abdominal cramps, watery diarrhoea and nausea	Meats, poultry, gravy, dried or precooked foods
Escherichia coli (STEC)		2 - 10 days more commonly 3 - 4 days	Diarrhoea (often bloody), abdominal cramps	Improperly cooked beef, unpasteurised milk and juice, sprouts and contaminated water
Hepatitis A		2 - 7 weeks	Jaundice, fatigue, anorexia, nausea	Raw or poorly cooked seafood harvested from contaminated waters, ready-to-eat foods handled by an infected food handler
Listeria monocytogenes		3 days - 10 weeks	Meningitis, sepsis, fever	Soft cheeses, unpasteurised milk, ready-to-eat deli meats
Norovirus		24 - 48 hours	Fever, nausea, vomiting, abdominal cramps, diarrhoea and headache	Poorly cooked shellfish, ready-to-eat foods touched by an infected worker
Salmonella		6 – 72 hours, usually 12-36 hours	Headache, fever, abdominal cramps, diarrhoea, vomiting and nausea	Undercooked poultry, raw egg deserts and mayonnaise, sprouts, tahini
Staphylococus aureus toxin		0.5 – 8 hours	Sudden onset of vomiting and abdominal cramps	Cream deserts and pastries, potato salad
Vibrio parahaemolyticus		4–30 hours, usually 12-24 hours	Nausea, vomiting, abdominal cramps and watery diarrhoea	Undercooked or raw seafood.

*The foods shown in the table have previously been found to be the source of the pathogens listed. This does not mean that these foods are always unsafe to eat or that such pathogens are always present, however the foodsshould be purchased from a reputable supplier and handled with care.

**Image credits: Partnership for Food Safety Education (USA); Laboratory of Clinical and Epidemiological Virology, Catholic University of Leuven (Belgium); HealthNJ, Univesity of Medicine and Dentistry of New Jersey (USA).

5. How do bacteria get in food?

Some foods accommodate pathogens more than others.

• Bacteria, including pathogens, may be present on foods such as raw meat, poultry, seafood, eggs, uncooked rice, flour, raw vegetables and salads at the time of purchase.
• Other pathogens develop in food as a result of poor temperature control or spoilage.

Pathogens are also carried on the bodies of food handlers.  Pathogens are frequently present in the throat, nose, skin, hair and faeces.  Pathogens can be transferred to food by touching hair or the nose, or smoking without washing hands before handling food. Sneezing or coughing around or near food can also lead to contamination.

This means food handlers can bring potentially harmful bacteria into food preparation areas and contaminate food.

Prepared foods including cooked and ready-to-eat foods may become contaminated with potentially harmful bacteria either directly via unclean surfaces or indirectly when bacteria are transferred from raw products or food handlers with poor personal hygiene.

6. Who is at risk?

In many cases the effects of foodborne illness are only mild but sometimes the symptoms can lead to serious illness. In rare cases, foodborne illness can result in long-term health problems and even death. Some people are extremely vulnerable, no matter what type of pathogen is involved. These include:

• Very young children
• Pregnant women,
• The elderly and
• People with compromised immune systems.

Some people may become ill after ingesting only a few harmful organisms while others may remain symptom free after ingesting thousands.

7. How to reduce the risk?

Personal Hygiene

Wash your hands thoroughly with soap and running water for at least 15 seconds and dry them with a clean towel before eating or preparing food.

Make sure you wash your hands thoroughly after:

• Using the toilet,
• Changing nappies,
• Smoking
• Blowing your nose
• Coughing or sneezing into hands
• Cleaning surfaces or waste

People with symptoms of foodborne disease especially vomiting or diarrhoea should not prepare food for others for 48 hours after the symptoms have finished. Temperature control Storing food at incorrect temperatures known as the “temperature danger zone” ie: above 5°C or below 60°C, can result in the multiplication of bacteria that cause foodborne illness.

As a precaution, ensure that :

• Refrigerators are kept below 5ºC with adequate air flow around food to ensure even temperature distribution;
• Hot foods are kept above 60°C (i.e. “steaming” hot).
• Cooked foods are reheated, should be reheated rapidly until all parts of the food reach 75°C.
• Frozen foods are thawed in either the refrigerator or the microwave. The longer raw food is left at room temperature the more quickly bacteria multiply and toxins may form. Avoid thawing foods on the bench.
• Remember that while the inside of the food may still be frozen, the outside may have thawed and is already in the “temperature danger zone”.
• Food needs to be thoroughly cooked to kill germs.

Storage Raw meat, fish, poultry, and raw vegetables can contain large numbers of bacteria, and can cross-contaminate ready-to-eat food if they are not stored or handled carefully.

It is advisable to:

• Store raw foods in covered or sealed containers below other ready-to-eat foods inside the refrigerator to prevent food parts and meat juice spilling or dripping on to other food;
• Cover foods before storage in the refrigerator, freezer, and cupboards to protect them from contamination;
• Wash hands immediately after handling raw foods and before handling cooked or ready-to-eat food;
• Do not wash meat such as raw chicken before cooking;
• Use different chopping boards, utensils, and plates for raw foods and ready-to-eat food. If the same chopping board or knife is used ensure it is washed thoroughly in hot soapy water and dried before re-use;
• Thoroughly wash raw vegetables before preparation and eating;
• Store food items carefully away from toxic chemicals, insect sprays, cleaning agents, etc;
• Don’t use cloth towels which have been used to wipe hands or bench tops for drying dishes. These should be washed and dried regularly;
• Regularly wash or replace dish cloths.

Remember: If uncertain about the quality or safety of a particular food, the old saying applies, ‘If in doubt, throw it out’.

8. Exposing foodborne illness “myths”

Most people believe they understand the basics of foodborne illness and are quick to blame a particular food for their illness. Investigation has shown, however, that correctly attributing a specific food as the cause of illness is very difficult.  The reality is people rarely identify the correct culprit for a number of reasons.

A few foodborne illness “myths”:

1.  I was sick after eating a certain food so it must have been that food that made me sick.

Symptoms of foodborne illness, particularly vomiting, can occur within a short time after the consumption of contaminated food. The last meal you ate may well have made you sick.  But it is also possible that the illness was due to another food consumed prior to your last meal.  Onset periods after consumption of the contaminated food will vary according to the type of pathogen so you will need to consider all the foods eaten over the past 3 days. (see "Types of foodborne illness" for a list of onset times and pathogens).

2.  I can get diarrhoea within a few hours after eating contaminated food.

Usually diarrhoea from a contaminated food does not start until at least 4-6 hours after having eaten that food and can be as long as 3 days after consumption.  So if you experience diarrhoea in less than 4 hours of eating it is most unlikely to be that meal which made you sick as a result of "food poisoning". You need to consider the previous meal or even food you ate the day before.

3. The food which I brought up when I vomited must have been responsible for my illness.

The food material present when you vomit is not always an indication of the food responsible for your illness. It is merely the stomach content at the time of onset.  The food responsible for your illness may have been consumed a day or so before the symptoms appeared.

4.  I was sick after eating so it must be “food poisoning".

Contaminated food can be the cause of gastrointestinal illness. But it is not the only cause.

• Contaminated water can also cause similar symptoms, such as during exposure at contaminated swimming pools.
• Viral illnesses are also a common cause and can be contracted from family and friends. Viral gastroenteritis which can cause vomiting and diarrhoea for about 2 days can be spread from one person to another.  Viral gastroenteritis is very contagious and can be transmitted while you are at dinner with them, visiting friends or living in the same house as someone who is already infectious.

Good hand washing and personal hygiene can help reduce the risk of person to person spread of viral illness.

5. The food must have made me sick because it smelt or tasted bad.

It is a common misconception that in order to get sick from food it must look, taste or smell bad or be “off”.

In fact, most food poisoning bacteria do not cause foods to appear bad.  There can be enough harmful bacteria in food to make you sick even though the food still seems normal in appearance, taste and odour.

The reverse situation is also true: there are some types of bacteria that will spoil food but will not make you sick if you accidentally eat it. The best option is “if in doubt about the condition of the food then don’t eat it”.