The most common causes of food poisoning include Campylobacter, Salmonella and Norovirus from eating contaminated food.
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What Are the Most Common Causes of Food Poisoning?
Food poisoning is one of the most common infectious diseases, affecting millions of people in the UK each year. Most often, it is caused by eating food contaminated with viruses or bacteria, such as E. coli, Salmonella, and Campylobacter, but there can be other causes.
Understanding the most common causes of food poisoning and how you can contract a foodborne illness can help you identify and avoid risk factors to prevent food poisoning and other food-related illnesses.
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How common is food poisoning?
Foodborne illnesses are very common. According to the Food Standards Agency (FSA), approximately 2.4 million cases of food poisoning occur each year in the UK, with numbers peaking during the summer months.
While most people only experience mild symptoms, others can become seriously unwell and may require hospital treatment. Furthermore, a study conducted on 11 key pathogens reveals that foodborne illnesses result in approximately 180 deaths annually.
The potential severity of these illnesses, along with the significant medical costs associated with them, underscores the importance of understanding the most common causes of food poisoning and the steps to prevent them.
What are the most frequent causes of food poisoning?
Food poisoning is an illness caused by consuming foods or drinks that are contaminated with harmful bacteria, parasites, viruses or toxins. The most common causes of foodborne diseases are bacteria and viruses, such as:
Campylobacter
Campylobacter is the most common cause of bacterial food poisoning in the UK (around 280,000 cases each year). The spiral-shaped bacterium is frequently found in raw or undercooked poultry, unpasteurised milk, shellfish and untreated water.
The symptoms of a Campylobacter infection (Campylobacteriosis) typically appear within 24 to 72 hours after consumption and include abdominal cramps, nausea, fever and diarrhoea (sometimes bloody).
Most people recover fully within a week, but Campylobacteriosis can cause serious health problems and long-term conditions such as irritable bowel syndrome (IBS) or Guillain-Barré syndrome.
Clostridium perfringens
Clostridium perfringens is the second most common cause of bacterial foodborne illnesses in the UK, with approximately 85,000 cases reported each year. This type of bacteria grows rapidly in cooked foods that have been left out for too long and is linked to meats such as poultry, beef, and pork.
Symptoms of C. perfringens food poisoning include abdominal pain, diarrhoea and vomiting, and typically appear within 6 to 24 hours after ingestion. They usually resolve within a day or two, but can result in complications such as dehydration, gas gangrene and sepsis.
Salmonella
Salmonella food poisoning is quite common. In 2024, there were 10,388 cases of Salmonella infections, a 17.1% increase from 8,872 cases in 2023. There are over 2,500 strains of Salmonella bacteria, which can be found in eggs, poultry, meat, raw fruits or vegetables.
Symptoms typically develop within 6 to 72 hours and can persist for 4 to 7 days. These include vomiting, headache, fever, diarrhoea, nausea and stomach cramps, which usually improve on their own.
Sometimes, the symptoms can be more severe and result in complications such as severe dehydration, joint inflammation, conjunctivitis and sepsis.
Escherichia coli (E. coli) O157
Although many strains of E. coli are harmless to humans, those that produce toxins called Shiga toxins (STEC) can cause severe illness. The STEC strain is responsible for a significant number of E. coli food poisoning cases in the UK.
E. coli O157 is often linked to undercooked ground beef, fresh fruit, salad leaves, unpasteurised milk and juice. Symptoms can start any time between 1 and 14 days after infection and can last about a week. These include abdominal cramps, diarrhoea and fever.
In some cases, infected people can develop a severe condition called haemolytic uraemic syndrome (HUS), which can lead to kidney failure and death. In 2024, there were 12 deaths linked to E. coli infections.
Listeria monocytogenes
While a less frequent cause of food poisoning, Listeria is one of the most dangerous because of its high fatality rate. The bacterium is commonly found in smoked fish, soft cheeses, pâté, unpasteurised milk and ready-to-eat deli meats.
Symptoms can appear anywhere from 3 days to 10 weeks and include fever, headache, tiredness, diarrhoea, aches and pains. In healthy individuals, they typically resolve within a few days, but those at higher risk can develop complications such as meningitis and sepsis.
In 2024, 174 cases of listeriosis were reported in England and Wales. Of these, 142 were non-pregnancy cases, resulting in 28 deaths. Among the pregnancy-associated infections, 43.7% resulted in miscarriage or stillbirth.
Norovirus
Norovirus, also known as the winter vomiting bug, is a highly contagious virus that can spread rapidly through contaminated surfaces, food or water.
Symptoms usually start within 24 to 48 hours and include diarrhoea, nausea, vomiting, abdominal cramps, fever and headache. Complications are rare, but they can be severe and include dehydration, renal failure and encephalitis in children.
There are around 380,000 cases of norovirus linked to food in the UK each year. Outbreaks are common in restaurants, schools, and care homes.
Rotavirus
Rotavirus is the leading cause of acute infantile gastroenteritis in children worldwide, causing approximately 530,000 deaths every year. The virus can be transmitted through contaminated food, water or surfaces, and it typically causes symptoms within 24 to 48 hours.
Rotavirus vaccination in children has contributed to a significant drop in cases within the last decade. However, outbreaks still occur, typically causing watery diarrhoea, vomiting, feeling sick and a mild fever.
In England and Wales, there are an estimated 130,000 cases of rotavirus-induced gastroenteritis each year in children under the age of five. Of these, approximately 12,700 are hospitalised, and deaths are rare.
Other causes
Besides the common viruses and bacteria that cause food poisoning, other causes include:
- Parasites that can live in the intestines, such as Giardia duodenalis, Toxoplasma gondii and Cryptosporidium parvum.
- Chemical toxins, such as pesticides, heavy metals and mycotoxins produced by certain moulds that contaminate foods like grains and nuts.
Which foods most commonly cause food poisoning?
Almost any type of food or drink can theoretically become contaminated and cause illness if not handled or stored correctly. However, some foods are more commonly linked to food poisoning because they provide the ideal conditions for parasites, bacteria or viruses to grow.
High-risk foods include:
- Raw or undercooked poultry and meats.
- Raw or lightly cooked eggs.
- Unpasteurised milk and dairy products.
- Seafood and shellfish, such as mussels, oysters and prawns.
- Leafy greens and fresh produce.
- Deli meats and ready-to-eat foods, such as pre-packaged sandwiches.
- Cooked rice and pasta.
- Fruit juice that has not been pasteurised.
- Foods that are not adequately sealed or canned.
- Raw sprouts like mung bean, clover sprouts or alfalfa.
Who is most at risk of food poisoning?
Anyone can get food poisoning, but certain groups of people are more at risk of developing a serious illness. These include:
- Children under the age of five, whose immune systems are still developing.
- People 65 and older, because ageing weakens the immune system and slows recovery.
- Pregnant women, whose hormonal changes can reduce immunity. Certain infections can also affect the foetus and lead to miscarriage, premature birth or stillbirth.
- People with weakened immune systems, including those with chronic conditions like diabetes and cancer.
How can foodborne illnesses be prevented?
Food poisoning is often preventable by following several key principles of food safety:
- Wash your hands properly with soap for at least 20 seconds before eating and preparing food.
- Wash surfaces and cooking utensils thoroughly after each use and clean your fridge regularly.
- Wash fruits and vegetables before eating or cooking them.
- Have separate cutting boards for meats and vegetables.
- Cook food thoroughly and to the proper temperature to kill germs.
- Always keep cooked food separate from uncooked food.
- Refrigerate or freeze leftovers within two hours.
- Keep your refrigerator at 5°C or below and your freezer at -18°C or below.
- Avoid consuming foods that are past their expiration date or have an unusual look or smell.
- Reheat leftovers until they reach a temperature of at least 74°C.
What should I do if I get food poisoning?
If you develop symptoms of food poisoning, you should stay off work or school until you have not been sick for at least two days. In the meantime, get plenty of rest, drink lots of water to prevent dehydration and eat bland foods until you feel better.
If your symptoms are severe or you are pregnant, have a weakened immune system or are otherwise at risk, you should seek immediate medical attention.
If you suspect a specific restaurant or food product caused your illness, you should:
- Keep the original packaging, receipts and leftovers.
- Make a note of what you ate and where.
- Report your illness to the FSA and your local Environmental Health Department.
- Gather evidence such as test results and witness statements.
If your illness was caused by negligence, such as poor hygiene, improper food storage or contaminated food, you may be able to make a food poisoning compensation claim.
Key takeaways
Food poisoning is a common illness that affects millions each year. While the majority of cases are mild and resolve on their own, others need hospital care and can cause severe symptoms and complications.
The most common causes of food poisoning in the UK are Campylobacter, norovirus and Clostridium perfringens. High-risk foods include undercooked meat, unpasteurised dairy, and contaminated produce. Practising good hygiene, proper food preparation and safe storage are the best ways to prevent foodborne illness.
