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Knowledge Base » Food Hygiene » What are Foodborne Diseases?

What are Foodborne Diseases?

Last updated on 20th December 2023

We don’t often consider food as being a risk in our everyday lives. However, if something looks off or doesn’t smell and taste quite right, we tend to discard it. We instinctively know that it would be unpleasant, and we could potentially get sick.

But what about the things we cannot see, taste and smell in our food that could cause us harm? These invisible food safety hazards are microscopic germs that can cause many foodborne diseases (illnesses). Some of these food diseases can be mild, some severe, and in some cases they can be life-threatening.

According to the Food Standards Agency (FSA), approximately 2.4 million cases of foodborne illness occur every year in the UK, which is up from the 2009 estimate of approximately one million. Globally, an estimated 600 million (almost 1 in 10 people in the world) fall ill after eating contaminated food, and 420,000 die every year (World Health Organisation). These figures highlight the prevalence and seriousness of foodborne diseases across the globe.

Foodborne diseases are a risk that everyone should be aware of, especially food businesses and food handlers. They should know what foodborne diseases are and the causes, as they have a significant role to play in preventing illness. They also have legal duties, under the Food Safety Act 1990 and associated food safety and hygiene regulations, to ensure that any food provided to consumers is safe for them to eat.

This article will look at what foodborne diseases are, the symptoms and some examples of the pathogens involved.

Food truck burger

What are foodborne diseases?

According to the World Health Organisation (WHO):

“Foodborne diseases encompass a wide spectrum of illnesses and are a significant cause of morbidity and mortality worldwide. They are illnesses associated with the ingestion of food contaminated by bacteria, viruses, parasites and chemicals as well as bio-toxins”.

Most foodborne diseases (also known as foodborne illnesses, foodborne infections or food poisoning) are caused by microorganisms. These are living organisms that are ubiquitous and are so tiny they are only visible through a microscope. Microorganisms include bacteria, viruses, fungi and some parasites.

Microorganisms that can cause diseases are known as pathogens. These are biological hazards that can contaminate and poison food and make it unsafe to eat. If consumed, unpleasant symptoms will usually develop after a few hours. How long the illness lasts will depend on the pathogen involved.

What are the symptoms of foodborne diseases?

Food poisoning is the collective term for many different foodborne diseases caused by eating food contaminated with pathogenic microorganisms. As pathogens enter the body, they can rapidly multiply and cause infection. Some can also produce toxins, which can result in intoxication. Food poisoning can also be caused by eating food contaminated with chemical hazards.

Food poisoning usually occurs where food has not been handled, stored (chilled/frozen) or cooked properly. It can also be caused by eating food after its use-by date, by poor personal hygiene and by cross-contamination.

Therefore, anyone who handles food has a responsibility to ensure good food hygiene and safety at all times. These responsibilities are covered under numerous food hygiene and safety laws and must be complied with by all food handlers.

Food poisoning is highly unpleasant, and the symptoms can vary between individuals.

Certain people will be more at risk of food poisoning than others, for example:

  • Children under five years old.
  • Adults over 65 years old.
  • Those with weakened immune systems.
  • Expectant mothers.

In extreme cases, food poisoning can be life-threatening, especially for those who are more vulnerable. The severity of food poisoning will also depend on the species of microorganism and the number consumed.

Symptoms of food poisoning can occur in a matter of hours or weeks after eating contaminated food. The time between eating contaminated food and symptoms showing is known as the incubation period. Different microorganisms have different incubation periods.

Common symptoms of food poisoning include:

  • Diarrhoea.
  • Vomiting.
  • Nausea.
  • A high temperature (fever).
  • Headache.
  • Chills.
  • Aching.
  • Tiredness.
  • Stomach cramps.
  • Abdominal pain.

For most people, symptoms will pass after a few days, and they will make a full recovery.

Showing Symptoms Of Food Poisoning As They Suffer From A Foodborne Disease

The complete list of foodborne diseases

There are many different foodborne diseases people can contract as a result of eating contaminated food. Most of them are caused by bacteria and viruses.

Food handlers should be aware of the most common foodborne diseases, and you will look at some examples here.

Bacillus cereus

  • Microorganism responsible – A spore-forming bacterium that can produce toxins.
  • Where is it found? – In the environment and mainly in soil.
  • At-risk foods – Raw vegetables that have been in contact with soil, cereal products, herbs and spices, dried foods, dairy and meat products, sauces and soups. Cooked rice is one of the foods most associated with B. cereus, as well as leftovers.
  • Symptoms – The toxins produced by B. cereus can cause two types of gastrointestinal illness:
    – An emetic (vomiting) syndrome – Symptoms include vomiting, nausea and sometimes diarrhoea. They usually start 30 minutes to 5 hours after ingesting contaminated food and typically disappear in 6-24 hours.
    – A diarrhoeal syndrome – Symptoms include nausea, abdominal cramps and diarrhoea. They usually start 8-16 hours after ingesting contaminated food and typically disappear in 12-24 hours.
  • Prevention – B. cereus spores are heat-resistant and can survive cooking. Therefore, food must be cooked or reheated to the correct temperature. It can also grow in warm environments, so it is important to chill and store foods properly and not leave them at room temperature. Rice should never be reheated more than once.


  • Microorganism responsible – Bacteria that is the most common cause of food poisoning in the UK. Two species, C. jejuni and C. coli are responsible for most infections.
  • Where is it found? – In the gastrointestinal tract of mammals, including livestock and pets such as dogs and cats.
  • At-risk foods – Common in raw or undercooked meat, especially poultry (chicken), unpasteurised milk and untreated water. It does not usually grow in food, but only a few bacteria are needed to cause illness.
  • Symptoms – An infection with campylobacter is known as campylobacteriosis. The incubation period is typically 2-5 days, but it can be 1-11 days. It’s a flu-like illness, and symptoms can include diarrhoea (often bloody), fever, stomach cramps, headache, nausea and vomiting. Symptoms can be severe for those who are more vulnerable, e.g. infants, those with weakened immune systems and the elderly.
  • Prevention – Cooking food thoroughly and good hygiene practices can prevent the disease, e.g.:
    – Washing hands thoroughly before preparing food and especially after handling raw foods.
    – Preventing cross-contamination by using different equipment and surfaces for raw foods and cooked/ready-to-eat foods. Never wash meat or poultry.
    – Storing raw foods and cooked/ready-to-eat foods separately in the refrigerator.

Clostridium botulinum

  • Microorganism responsible – A bacterium, which can also produce a toxin in the absence of oxygen. The toxin can cause a condition known as botulism.
  • Where is it found? – In soil, dust, and river or sea sediments.
  • At-risk foods – common in prepared canned, bottled and vacuum-packed foods.
  • Symptoms – The time it takes for botulism symptoms to show varies, but they are severe. The toxin produced by the bacteria can attack the body’s nervous system, which can cause paralysis and can be fatal. Botulism is a serious emergency that requires immediate medical attention.
  • Prevention – Thankfully, botulism is very rare in the UK. Manufacturers of canned goods have to adhere to very high food hygiene and safety standards. There is a risk where individuals produce and can their own foods, which can be prevented by following good food hygiene and canning procedures. To prevent botulism, it is important to discard food from bulging or damaged cans and avoid eating foods that are:
    – Foul-smelling (preserved foods);
    – Stored at the incorrect temperature; and
    – Out of date.

Clostridium perfringens

  • Microorganism responsible – A spore-forming bacterium that can produce an enterotoxin.
  • Where is it found? – It is common in the environment and can also be found in faeces, as it forms part of the normal gut flora in humans and animals.
  • At-risk foods – It is typically found in meats, such as beef and poultry, and casseroles, meat pies and gravies. The risk increases when food is prepared in advance and kept warm for several hours before serving. It also gives the spores time to germinate and produce toxins in the food.
  • Symptoms – Include stomach pains and diarrhoea, which usually last for 12-24 hours. Fever and vomiting are unusual. The elderly are vulnerable to the disease.
  • Prevention – C. perfringens spores can survive normal cooking temperatures, as they are heat-resistant. Therefore, food must be cooked or reheated to the correct temperature. Also, the bacteria do not grow at refrigerated temperatures, so prompt chilling of food is essential if food is not eaten immediately. Food must be held at higher temperatures if waiting for it to be served.

Escherichia coli (E. coli)

  • Microorganism responsible – There are many different strains of E. coli bacteria. Some are usually harmless and play a vital role in the gut. Others can cause food poisoning and produce toxins.
  • Where is it found? – In the environment, and faeces and intestines of animals (particularly cattle) and humans. The bacteria are also in raw sewage and untreated water.
  • At-risk foods – Common in undercooked beef (particularly minced), contaminated water, unpasteurised milk and raw fruits/vegetables. The food contaminated will depend on the species involved.
  • Symptoms – Include low-grade fever, vomiting, fatigue, abdominal pain and diarrhoea (sometimes bloody). The incubation period is usually 3-4 days after exposure but can be as short as one day or as long as ten days. Those who are vulnerable, e.g. the elderly, those with weakened immune systems and young children, are particularly at risk of infection.
  • Prevention – Maintaining strict personal hygiene and preventing cross-contamination are vital in preventing E. coli infections. Raw unpasteurised milk should be avoided. Beef must be cooked thoroughly, especially minced products.

Escherichia coli O157

  • Microorganism responsible – A bacterium, which is a different strain of E. coli and more dangerous. It is known as VTEC, as it produces toxins that can cause severe illness and can be fatal.
  • Where is it found? – In the faeces and intestines of animals (particularly cattle) and humans. It can also be transmitted from person-to-person.
  • At-risk foods – Common in raw and undercooked meats, raw leafy vegetables and salads, untreated water or unpasteurised milk.
  • Symptoms – Include fever, abdominal cramps, nausea, vomiting, and bloody diarrhoea. These are usually seen 3-4 days after infection. However, symptoms can be experienced for 1-14 days and can last up to two weeks. The toxin can destroy red blood cells, and sufferers can develop a condition known as haemolytic uraemic syndrome (HUS). This is rare, but it can lead to kidney failure and death. Children under five years old are at a higher risk of HUS.
  • Prevention – Poor personal hygiene standards and cross-contamination are the main reasons for infections. Therefore, strict food hygiene practices must be followed. The Food Standards Agency has guidance on avoiding E. coli O157 and E. coli and cross-contamination.

Listeria monocytogenes

  • Microorganism responsible – A bacterium that causes an infection known as listeriosis. Infections are rare but can be serious. It is not like other bacteria, as it can grow at low temperatures, including refrigeration temperatures of below 5°C.
  • Where is it found? – Widespread in the environment, e.g. soil, water, and decaying vegetation.
  • At-risk foods – It is found in a wide range of foods, e.g. unpasteurised milk and dairy products, soft cheeses, salads, chilled ready-to-eat foods (deli meats and pate), and raw/undercooked meat, poultry and seafood.
  • Symptoms – Some people have mild symptoms for a few days. Others may experience a high temperature of 38°C or above, aches and pains, chills, feeling or being sick and diarrhoea. It can severely affect vulnerable people, e.g. pregnant women, the elderly, infants, and those with weakened immune systems. In some cases, it can also be fatal due to complications, such as meningitis.
  • Prevention – Listeria is killed by heat and pasteurisation. Good food hygiene practices must be followed, including:
    – Avoiding cross-contamination.
    – Washing raw vegetables, salad and fruit well.
    – Cooking and reheating foods thoroughly.
    – Strictly following storage instructions and never eating food after its use-by date.
    – Further advice on listeria.


  • Microorganism responsible – A virus, which is also known as the winter vomiting bug. According to the Food Standards Agency, it causes an estimated three million cases of diarrhoea and vomiting each year. In the UK, 380,000 cases are linked to food every year.
  • Where is it found? – It is spread by humans via the faecal-oral route to food and drinks, usually through poor hygiene practices. It is highly contagious.
  • At-risk foods – It is common in shellfish, leafy vegetables, fruit and ready-to-eat foods. Norovirus does not multiply in food, but it can survive on it for long periods.
  • Symptoms – Norovirus has an incubation period of 12-48 hours. Symptoms can vary, but the main ones are vomiting, nausea, abdominal pain and diarrhoea. It is a mild illness, albeit unpleasant, that usually goes away after two days. It can be dangerous for more vulnerable people, such as the elderly, due to dehydration.
  • Prevention – Foods like shellfish should be cooked thoroughly, and those who are vulnerable should avoid raw seafood. Good hygiene practices, including personal hygiene, are essential in preventing norovirus transmission, e.g.:
    – Washing hands frequently and thoroughly.
    – Washing raw vegetables, fruits and salad.
    – Thorough cleaning and disinfection of surfaces and equipment.
    – Food handlers who have been ill should stay away from work until at least 48 hours after the last episode of diarrhoea or vomiting.
A Chef Ensuring All Surfaces Are Clean To Prevent Any Foodborne Diseases


  • Microorganism responsible – According to Public Health England, there are more than 2,500 strains of salmonella bacteria, and it is a common cause of food poisoning. Salmonella causes an infection known as salmonellosis.
  • Where is it found? – In the intestines and faeces of humans and animals (including pets). It can also be spread from person-to-person.
  • At-risk foods – It is found in a wide variety of foods, but most common in raw meat, undercooked poultry, unpasteurised milk, cheese and undercooked eggs. The bacteria are usually spread by inadequate cooking and cross-contamination.
  • Symptoms – Include diarrhoea, stomach cramps, nausea, vomiting and fever. Symptoms develop in 12-72 hours, and the illness can last for 4-7 days. Those who are vulnerable are at a higher risk of becoming unwell and may require treatment.
  • Prevention – Infection occurs through contaminated food or water. Therefore, following good hygiene practices and the 4Cs of food hygiene (cleaning, cross-contamination, cooking and chilling) can prevent infection. You can learn more about salmonella poisoning by accessing out knowledge base.


  • Microorganism responsible – A family of bacteria that can cause an infection known as shigellosis or bacillary dysentery. There are four species of shigella: Shigella sonnei, Shigella flexneri, Shigella boydii and Shigella dysenteriae. Two out of the four species responsible for shigellosis are found in the UK (S. sonnei and S. flexneri).
  • Where is it found? – Human and animal intestines, faeces and contaminated water and food.
  • At-risk foods – It is often spread from person-to-person via the faecal-oral route. It is common in salads (especially potato, seafood, meats or pasta), raw vegetables and fruit, milk and dairy products, poultry or contaminated water.
  • Symptoms – Usually begin 12 hours to 2 days after infection and can last up to a week. They include fever, stomach cramps, vomiting and diarrhoea (sometimes bloody).
  • Prevention – Shigella is typically associated with travel to countries where sanitation and hygiene standards are poor. Food handlers should declare if they have travelled to high-risk areas and if they have any symptoms. Dysentery is highly contagious. Therefore, strict personal hygiene is crucial in preventing the spread of the disease. Luckily, foodborne infections involving shigella are rare in the UK.

Staphylococcus aureus

  • Microorganism responsible – A bacterium that can produce toxins. Staphylococcal (Staph) food poisoning occurs after ingesting these toxins.
  • Where is it found? – On people’s skin, hair, wounds, sores, septic spots and in the nose. It can be transferred to food by poor hygiene practices and by coughing or sneezing. Some people carry the bacteria naturally.
  • At-risk foods – Found in cooked meats and poultry, unpasteurised dairy products and hand-made ready-to-eat foods.
  • Symptoms – Usually develop within 30 minutes to 8 hours after eating or drinking an item containing the toxin. Symptoms include sudden vomiting, nausea, stomach cramps and diarrhoea. The illness typically lasts for one day.
  • Prevention – Good food hygiene practices must be followed, e.g. thorough cleaning of surfaces and equipment. Strict personal hygiene of food handlers is also vital in preventing S. aureus infections, e.g.:
    – Washing hands regularly and thoroughly before preparing food and after touching skin, sneezing or coughing.
    – Covering cuts and sores with brightly coloured waterproof plasters and dressings when preparing food.

Typhoid fever

  • Microorganism responsible – A bacterium known as Salmonella typhi causes typhoid fever. It is related to the bacteria that causes salmonellosis.
  • Where is it found? – In human intestines, faeces and urine. An infected person can contaminate food, water, surfaces and equipment. It is spread through the faecal-oral route from infected individuals and asymptomatic carriers of the bacteria. Typhoid Mary is the most famous example of an asymptomatic carrier infecting others.
  • At-risk foods – Food that has been washed in contaminated water, e.g. seafood and raw fruit and vegetables. Contaminated milk products can also be affected.
  • Symptoms – The incubation period is usually 1-2 weeks, with the illness lasting 3-4 weeks. Symptoms include fever, weakness, abdominal pain, constipation, headaches, and mild vomiting. It can cause serious complications and can be fatal if left untreated.
  • Prevention – Typhoid fever is highly contagious. However, it is uncommon in the UK. It is more prevalent in countries with poor sanitation and hygiene. Therefore, people travelling to these countries are at a higher risk. Like shigella, any food handlers travelling to high-risk countries must declare this and report any symptoms. Strict personal hygiene rules must always be followed.


There are many different microorganisms which can contaminate our food and drink and cause foodborne diseases. As you have seen, some can cause mild unpleasant illnesses. However, some can be severe and even life-threatening. This is particularly the case where toxins are involved and where those who are more vulnerable are infected.

Food businesses and food handlers have legal duties to ensure food is safe for consumers. These duties include preventing and controlling the food safety hazards that can cause foodborne diseases. Adopting the best food hygiene practices and following the 4Cs of food hygiene can keep those with legal responsibilities on the right side of the law.

The symptoms of food poisoning are very similar, regardless of which pathogen is involved. Therefore, individuals should always seek medical advice if they have any concerns about their condition worsening.

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About the author

Michelle Putter

Michelle Putter

Michelle graduated with an MSc in wildlife biology and conservation in 2012, but her career has taken quite a different turn to the one expected. She started in health and safety in 2009 and has worked in several industries such as electrical engineering, aviation and manufacturing. She has been working with CPD Online College since 2018 and became NEBOSH Diploma qualified in 2020. In her spare time, Michelle's passions are wildlife and her garden. She has volunteered for many conservation organisations and particularly enjoys biological recording. Michelle also likes hiking, jogging and cycling.

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