Foodborne Illness: Common Causes, Symptoms and Prevention

Foodborne illness is caused by eating food contaminated with harmful bacteria, viruses, parasites or toxins. In the EU, Campylobacter, Salmonella, Shiga toxin-producing E. coli and Listeria are major causes. Food businesses prevent illness through effective cooking, chilling, cleaning, cross-contamination controls and procedures based on Regulation (EC) No 852/2004.

Foodborne illness—often called food poisoning—covers diseases caused by consuming contaminated food or drink. The hazard may be biological, such as bacteria or viruses, but illness can also result from parasites, naturally occurring toxins or chemical contamination. Contamination can happen during production, processing, transport, storage, preparation or service.

The scale of the problem remains significant. The European Food Safety Authority (EFSA) and European Centre for Disease Prevention and Control (ECDC) recorded 6,558 food-borne outbreaks in 2024, involving 62,481 reported cases, 3,336 hospitalisations and 53 deaths. Campylobacteriosis was the most frequently reported zoonosis, followed by salmonellosis, while Listeria monocytogenes caused the highest proportions of hospitalisations and deaths among the monitored foodborne infections.

In brief:

• Food can look, smell and taste normal while still containing harmful microorganisms.

• Symptoms and onset times differ substantially between pathogens.

• Poultry, eggs, raw meat, unpasteurised products and certain chilled ready-to-eat foods require particularly strong controls.

• Effective prevention depends on a complete food-safety system, not one isolated temperature check or cleaning task.

• National requirements may add to the common EU hygiene framework.

This article provides general food-safety guidance, not medical or legal advice. Individual Member States and regional authorities may impose additional requirements.

What is foodborne illness?

Key takeaway: Foodborne illness occurs when contaminated food or drink exposes a person to a harmful biological, chemical or toxic agent.

A foodborne illness may be an infection, an intoxication or a combination of both. An infection occurs when a person consumes viable pathogenic microorganisms that then multiply or act inside the body. An intoxication occurs when a person consumes a toxin already present in the food.

The everyday term “food poisoning” is commonly used for both, but the distinction matters during an investigation. A bacterial infection may point towards undercooking, contaminated ingredients or cross-contamination. A toxin-related incident may instead involve incorrect storage, unsuitable raw materials, chemical contamination or bacterial growth before the food was eaten.

Under Regulation (EC) No 852/2004, food business operators are responsible for complying with hygiene requirements at the stages of the food chain under their control. The Regulation requires appropriate hygiene arrangements and, outside primary production, permanent procedures based on Hazard Analysis and Critical Control Point principles where applicable. It also addresses staff supervision, instruction and training.

The European Commission describes the EU “Hygiene Package” as a harmonised framework applying across Member States. Regulation (EC) No 852/2004 sets general hygiene requirements, while more specific rules may apply to food of animal origin and particular sectors.

For a broader explanation of how these controls fit together, see the Food Hygiene and Safety: The Complete Guide for Food Businesses (EU).

What are the most common causes of foodborne illness?

Key takeaway: Campylobacter, Salmonella, pathogenic E. coli, Listeria and norovirus are among the most important causes for European food businesses to control.

The latest EFSA–ECDC EU One Health Zoonoses Report recorded 168,396 campylobacteriosis cases, 79,703 salmonellosis cases, 11,738 Shiga toxin-producing E. coli infections and 3,041 confirmed invasive listeriosis cases in 2024. Salmonella, norovirus and Campylobacter were also the most commonly identified causes of reported food-borne outbreaks.

Campylobacter

Campylobacter is the most frequently reported zoonotic cause of human illness in the EU. It is strongly associated with poultry, contaminated water and cross-contamination from raw poultry to hands, utensils, surfaces or ready-to-eat foods. Typical symptoms include abdominal pain, diarrhoea and fever, usually beginning two to five days after exposure.

The operational lesson is that cooking the chicken correctly is not enough if its packaging, juices, preparation board or handling equipment contaminate food that will receive no further cooking.

Salmonella

Salmonella causes salmonellosis and is the second most commonly reported zoonotic disease in the EU. It is frequently associated with eggs, poultry, pig meat and other raw animal products, although produce and mixed foods can also be implicated. Symptoms commonly include diarrhoea, fever and abdominal cramps.

In the 2024 EU outbreak data, Salmonella paired with eggs and egg products caused the highest number of outbreaks and hospitalisations among reported agent–food combinations.

Shiga toxin-producing Escherichia coli

Shiga toxin-producing Escherichia coli—usually shortened to STEC—can cause abdominal pain, vomiting and diarrhoea, which may be bloody. Symptoms generally begin three to eight days after exposure. The infective dose can be low, so small contamination events may still be significant.

Potential sources include undercooked minced meat, raw milk, contaminated fresh produce, untreated water and cross-contamination. Food businesses must therefore control both cooking and the transfer of contamination from raw ingredients or environments.

Listeria monocytogenes

Listeria monocytogenes causes listeriosis. Although reported case numbers are lower than those for Campylobacter or Salmonella, invasive listeriosis can be particularly severe for older adults, pregnant people, newborns and people with weakened immune systems.

Listeria is especially relevant to chilled ready-to-eat food because control cannot depend on reheating by the customer. Businesses must manage environmental hygiene, shelf life, storage temperatures, ingredient controls and contamination after cooking or processing.

Norovirus

Norovirus is a highly contagious cause of acute gastroenteritis. It can spread through contaminated food, water, hands, equipment and surfaces, as well as directly from an infected person. Symptoms commonly include sudden vomiting, diarrhoea and stomach pain, with an incubation period of approximately 12 to 48 hours.

For food businesses, ill-person reporting, exclusion procedures, effective handwashing and appropriate incident cleaning are essential. Gloves do not compensate for inadequate hand hygiene or an employee working while symptomatic.

What are the symptoms of food poisoning?

Key takeaway: Diarrhoea, abdominal pain, nausea, vomiting and fever are common, but symptoms alone cannot reliably identify the responsible pathogen.

Foodborne illness symptoms range from mild, short-lived gastrointestinal discomfort to severe infection requiring hospital care. The most common symptoms include:

• Diarrhoea

• Abdominal pain or cramps

• Nausea

• Vomiting

• Fever

• Headache, fatigue or muscle aches

• Dehydration resulting from fluid loss

The type and severity of illness depend on the pathogen, the quantity consumed, the person’s health and the time between contamination and consumption. Some infections can also lead to complications affecting the bloodstream, nervous system, kidneys, joints or pregnancy.

Symptoms should not be used by a food business to diagnose the cause of an incident. Similar symptoms can be produced by multiple pathogens, and an affected person may have eaten several meals during the relevant exposure period. Businesses should preserve records, retain relevant food samples where required, cooperate with the competent authority and avoid making unsupported claims about the cause.

Anyone concerned about symptoms, severe illness, dehydration or exposure during pregnancy should seek advice from an appropriate healthcare professional or public-health service. This article does not provide diagnosis or treatment guidance.

How long does foodborne illness take to develop?

Key takeaway: Onset may occur within hours or take several days or weeks, so the most recent meal is not necessarily the source.

Incubation time is the period between exposure and the appearance of symptoms. It varies by microorganism and can also vary between individuals.

For example, norovirus symptoms commonly appear within 12 to 48 hours, while Campylobacter symptoms usually begin after two to five days. STEC commonly has an incubation period of three to eight days. Non-typhoidal Salmonella symptoms often begin within 6 to 72 hours, usually 12 to 36 hours. Invasive listeriosis can take considerably longer, with ECDC describing an incubation period of about three weeks in many cases.

This variation matters during outbreak investigations. A customer complaint received on Monday may relate to food served at the weekend, earlier in the week or, in some cases, much earlier. Traceability, supplier records, cooking logs, storage records, staff rotas and cleaning records help investigators reconstruct what happened without relying solely on memory.

Which foods and people are at higher risk?

Key takeaway: Risk depends on the food, the process, the opportunity for contamination and the vulnerability of the person consuming it.

Foods requiring particularly careful control commonly include:

• Raw or undercooked poultry

• Eggs and foods containing insufficiently cooked egg

• Raw or undercooked minced meat

• Unpasteurised milk and products made from it

• Chilled ready-to-eat meats, fish or dairy products

• Cooked foods handled after their final heat treatment

• Prepared salads, cut produce and other ready-to-eat foods

• Sprouted seeds and produce exposed to contaminated water

• Mixed foods assembled from several cooked and uncooked components

EFSA identifies raw poultry and cross-contamination from poultry as major Campylobacter risks. It also identifies eggs and raw meat as important Salmonella sources, while EU outbreak data continue to highlight eggs, mixed foods and ready-to-eat categories as relevant vehicles.

People at greater risk of severe illness

Foodborne disease can affect anyone, but the consequences may be more serious for:

• Infants and young children

• Older adults

• Pregnant people and unborn babies

• People with weakened immune systems

• People with significant underlying health conditions

These groups are particularly important when food is prepared for hospitals, care settings, nurseries or other services supporting vulnerable consumers. Listeriosis is a specific concern because it can cause severe bloodstream or neurological infection and serious pregnancy complications.

Country variations: Regulation (EC) No 852/2004 provides the common EU hygiene framework, but Member States may have additional rules on training evidence, official inspections, food-service controls, microbiological sampling and particular retail or catering activities. Businesses should verify the requirements imposed by their national, regional and local competent authorities.

For more focused guidance, see High-Risk Foods: What They Are and How to Handle Them Safely.

How do foodborne illness outbreaks happen?

Key takeaway: Outbreaks usually arise from a chain of control failures rather than one isolated mistake.

A food-borne outbreak occurs when multiple cases are linked to a common food or food-handling event. The practical causes commonly involve one or more of the following:

1. Contaminated ingredients enter the business.
   Raw poultry, eggs, produce, ready-to-eat ingredients or water may already carry a hazard.

2. The hazard is not destroyed or reduced.
   Food is undercooked, reheated inadequately or processed using an unvalidated method.

3. Microorganisms are allowed to multiply.
   Cooling is too slow, refrigeration is ineffective, hot holding fails or food remains outside controlled conditions for too long.

4. Contamination spreads.
   Raw ingredients, hands, cloths, probes, utensils, packaging or equipment contaminate cooked or ready-to-eat food.

5. An infected food handler contaminates food.
   Poor handwashing, ineffective sickness reporting or premature return to work allows viral or bacterial contamination.

6. The business cannot detect or contain the problem.
   Missing records, weak traceability and unclear corrective-action procedures delay withdrawal, recall or investigation.

A recurring operational weakness is focusing on the visible food while overlooking contact points. A cooked product may be safe when it leaves the oven but become contaminated by the tray, probe, handle, garnish station or employee who handles it afterwards.

The 2024 EU data show why these combined controls matter: reported outbreaks, cases and hospitalisations all increased compared with 2023, and multi-country outbreaks continued to be associated with widely distributed food products.

How can foodborne illness be prevented?

Key takeaway: Prevention requires validated controls for cooking, chilling, cleaning and cross-contamination, supported by trained staff, records and corrective action.

The “4Cs”—cooking, chilling, cleaning and avoiding cross-contamination—provide a useful operational structure. They are a practical mnemonic rather than a defined legal formula in Regulation (EC) No 852/2004.

1. Cook and reheat using validated limits

Businesses should identify which foods require a pathogen-reduction step and establish appropriate time-and-temperature or equivalent process limits. The correct limit may depend on the food, process and national guidance.

Staff should:

• Measure the relevant part of the food, normally its core or coldest point.

• Use a clean, suitable and calibrated probe.

• Record results where monitoring is necessary.

• Take defined corrective action when the limit is not achieved.

• Avoid assuming that colour or appearance proves safety.

See The Temperature Danger Zone and Safe Food Temperatures for deeper temperature-control guidance.

2. Control chilling, cooling and storage

Cold storage slows the growth of many microorganisms but does not make contaminated food safe. Cooling methods should prevent cooked food remaining warm for unnecessarily long periods, and refrigeration equipment should be monitored against the business’s defined limits.

Businesses should also control shelf life, stock rotation, thawing, delivery temperatures and the time food spends outside refrigeration.

3. Prevent cross-contamination

Separate raw food from cooked and ready-to-eat food throughout delivery, storage, preparation and service.

Effective measures include:

• Physically separated preparation areas where practicable

• Dedicated or properly disinfected equipment

• Controlled movement of staff and utensils

• Safe storage hierarchy

• Cleaning and disinfection between tasks

• Handwashing at the correct times

• Procedures for food probes, cloths, handles and touch points

See Cross-Contamination in the Kitchen: Types, Causes and How to Prevent It.

4. Clean and disinfect effectively

Cleaning removes food debris, grease and other contamination. Disinfection reduces microorganisms to an acceptable level when applied under the correct conditions. The two activities are related but not interchangeable.

A cleaning plan should state:

• What must be cleaned

• Who is responsible

• Which product and concentration to use

• Required contact time

• Method and frequency

• Safety precautions

• How completion and effectiveness are checked

5. Manage staff illness and hygiene

Food handlers should understand when and how to report vomiting, diarrhoea, infected wounds or other relevant symptoms. Managers need a clear escalation and return-to-work procedure aligned with national public-health guidance.

Handwashing facilities, protective clothing and supervision must support the procedure. Training without the necessary time, equipment or management enforcement will not control the risk.

6. Verify the food-safety system

Regulation (EC) No 852/2004 requires food business operators to implement hygiene controls and applicable procedures based on HACCP principles. Codex Alimentarius’ General Principles of Food Hygiene provides recognised international good-practice guidance on food hygiene and HACCP, but Codex texts are not themselves EU legislation unless incorporated through applicable law or requirements.

Verification may include:

• Record review

• Probe calibration

• Cleaning inspections

• Microbiological or environmental sampling where appropriate

• Observation of staff practices

• Supplier-performance review

• Complaint and incident trending

• Review after menu, process or equipment changes

For a broader implementation framework, see The 4 C's of Food Safety Explained (Cleaning, Cooking, Chilling, Cross-Contamination).

Pathogen quick-reference table

Key takeaway: Each pathogen has different sources and onset patterns, but all require systematic ingredient, hygiene, process and staff controls.

The onset periods are general reference ranges rather than diagnostic rules. Official investigation and laboratory evidence are needed to identify the cause of an incident.

Prevent Foodborne Illness Through Competent Food-Safety Practice

Effective food-safety controls depend on staff understanding not only what procedure to follow, but why the control matters, how it is monitored and what action to take when it fails.

Explore the Food Hygiene and Safety course to strengthen practical knowledge of contamination control, hygiene, temperature management, cleaning and organisational food-safety responsibilities.