Bacteria and viruses that can cause food poisoning

Updated: Jul 24, 2021

24th April 2020 by David Lee

In this article

  • Salmonella

  • Campylobacter

  • Bacillus cereus

  • Clostridium Perfringens

  • Clostridium Botulinum

  • Staphylococcus Aureus

  • Listeria Monocytogenes

  • Escherichia Coli 0157 (E.Coli)

  • Novovirus

  • Typhoid

Food poisoning is a general term that we use when someone consumes food or drink that makes them ill. But there is not just one type of food poisoning. In fact, there are numerous types of bacteria and viruses that can cause illness if they contaminate something we consume.

Food poisoning is very serious. Around 1 in 10 people fall ill with food poisoning every year and this can be very serious, especially in young children and vulnerable groups. Here we will look at the types of bacteria and viruses that come under the umbrella term of ‘food poisoning’ and the types of foods they are likely to contaminate.


Salmonella is a bacterial disease that affects a persons intestinal tract. It is quite common and one of the most referred to forms of food poisoning. Humans can be affected by salmonella poisoning through the consumption of not only contaminated food but water also. Although it is quite common, salmonella poisoning can be very dangerous. Sometimes it can be so bad that the person may become dangerously dehydrated and require medical attention.


Sources of salmonella can be raw meat and poultry, raw milk, raw eggs, fruit and salads, pets and rodents, flies, sewage and water. Salmonella can also be found in the human intestines during some illnesses.

Where do you find it?

Undercooked meat and poultry, raw milk, raw eggs and contaminated food. Can be present in uncooked product which uses raw eggs in preparation (mayonnaise and mousses).

Onset period and symptoms

Salmonellas onset period is usually 6 to 72 hours and symptoms can include abdominal pain, diarrhoea, nausea, vomiting and headache. Duration of symptoms is usually 1 to 7 days after which the sufferer may remain a carrier of the bacteria for a period.


Campylobacter is one of the most common cause of food poisoning & acute diarrhoea in the UK. It causes campylobacteriosis which results in a number of symptoms and can lead to dehydration. Raw chicken consumption is one of the most common causes of someone being affected by campylobacter.


Raw poultry (most common cause), raw meat and milk, farm animals, pets, birds, sewage and untreated water.

Where do you find it?

Raw and undercooked poultry and meat, undercooked liver paté, raw milk, bottled milk pecked by birds and contaminated water. Cross contamination from poultry is very likely and hands can carry campylobacter for up to an hour.

Onset period and symptoms

Onset period is between 1 and 10 days and duration of illness is normally 2 to 7 days. Symptoms include headache, fever, diarrhoea (often bloodstained), abdominal pain and nausea.

Bacillus cereus

Next up we have Bacillus cereus which is a toxin-producing form of bacteria. It is found in soil and the environment but, with many things we eat being grown in the ground, can easily be passed on to foodstuffs. Bacillus cereus multiples very quickly at room temperature so a food that is contaminated can quickly reach dangerous levels when left out.


Cereals, especially rice, dried food, spices, vegetation, soil and intestinal tracts of humans.

Where do you find it?

Reheated rice (especially if cooling period after cooking is too long or is kept at ambient temperature). Can be found in cornflour products, custards and pastries, vegetable dishes, meats and starchy foods such as pasta. Bacillus Cereus can form spores, which may multiply and will survive normal cooking temperatures.

Onset period and symptoms

Bacillus cereus has an onset period of 1 to 6 hours and illness usually lasts for 1 to 2 days. Symptoms include nausea, vomiting, abdominal pain and diarrhoea.

Clostridium Perfringens

Clostridium Perfringens , commonly known as C. Perfringens, is a spore-forming bacteria that can be found on raw meat and poultry. It can also divide very rapidly and even grows faster in conditions with little or no oxygen.


This can be found in humans and animals intestines, faeces and sewage, soil and sources can also include insects, raw meat and poultry.

Where do you find it?

Clostridium Perfringens can occur in casseroles, stews and sauces, mince, meat pies and can produce spores during cooking and long, slow cooling which can then survive cooking at high temperatures and dehydration.

Onset period and symptoms

The onset period for Clostridium Perfringens is 4 to 24 hours and illness usually lasts 12 to 48 hours. Symptoms include abdominal pain and diarrhoea.

Clostridium Botulinum

Clostridium Botulinum is another type of bacteria which can divide in environments with little or no oxygen. This type of food poisoning is rare but can be extremely serious because it can block nerve functions and result in respiratory paralysis.


The intestines of fish and animals soil and vegetables can contain clostridium botulinum.

Where do you find it?

Processed food, compromised tinned or vacuum packed meat or fish including smoked or fermented, and products containing mascarpone cheese and dried milk.

Onset period and symptoms

Commonly two hours to eight days and symptoms may last several months. Symptoms include difficulty in swallowing, talking and breathing, double vision and muscular paralysis. Fatalities are common and survivors may take several months to recover.

Staphylococcus Aureus

Staphylococcus Aureus (commonly called Staph infection) is a little different to the other types of bacteria we have looked at so far because it is passed on from people. This means that food is often contaminated by people when handling and is most dangerous in food that is handled and consumed without cooking to kill the bacteria.


Nose and ears, mouth, skin, hands, abrasions and boils can lead a person with a staph infection to contaminate others. Raw milk or products such as cheese made from raw milk. Staphylococcus Aureus is carried by a significant proportion of the population in their mouth or nose.

Where do you find it?

Milk and dairy products, desserts, custards, cold cooked meat and poultry, cooked prawns and fermented sausage.

Onset period and symptoms

Onset period 1 to 7 hours duration of illness usually between 6 and 24 hours. Symptoms include abdominal pain, nausea, vomiting, diarrhoea, collapse, and occasionally subnormal temperatures.

Listeria Monocytogenes

In adults, Listeria Monocytogenes can cause flu-like symptoms and be very serious in vulnerable groups such as the elderly, pregnant women and those with a weakened immune system. The types of food which listeria can contaminate is very varied.


Soil, and sewage, water, vegetation, animals and people.

Where do you find it?

Irrigation water, effluent, and sewage sludge. The Listeria bacteria can come from human and animal carriers and may be transmitted by excretion resulting in cross contamination. Other vehicles include unwashed fruit and vegetables, raw meat and products made from raw milk.

Onset period and symptoms

Incubation period is between 1 day and 3 months for listeria. Symptoms are flu-like including a fever, diarrhoea, vomiting, septicaemia, meningitis and abortion. The disease mainly affects older people, those with a weak immune system, pregnant women and newborn children.

Escherichia Coli 0157 (E.Coli)

E.Coli is another fairly well-known type of bacteria which is found in the intestines of animals and humans. Most strains are harmless but E.Coli can live outside the body so food can be contaminated.


Human and animal intestines, sewage and untreated water.

Where do you find it?

Undercooked burgers and mince and other meat products, contaminated cooked meat, salad vegetables and fruit, raw milk and product and fruit juice can all contain E.Coli. A very low infective dose may cause illness and extra hygiene precautions should be taken should be taken after handling raw meat to prevent cross contamination.

Onset period and symptoms

The onset period is 1 to 10 days and duration of illness is approximately 7 to 10 days. Symptoms include watery diarrhoea, nausea, abdominal pain and severe abdominal cramps.


Norovirus is, as the name suggests, a virus and not bacteria. It is the most common viral form of food poisoning and results in vomiting and diarrhoea that will last 2-3 days. Norovirus can be passed through contaminated food as well as from person to person.


Infected people and animals, the environment and sewage can all be sources of norovirus.

Where do you find it?

Person to person transmission, shellfish, salad vegetables and fruit.

Onset period and symptoms

Norovirus has an onset period of 10 to 50 hours, and symptoms can last around 12 to 60 hours. Symptoms include vomiting (projectile), diarrhoea, abdominal pain, fever, nausea and dehydration.


Typhoid is related to salmonella and its scientific name is salmonella typhi. With this type of infection, fever, headaches and abdominal pain is common but diarrhoea is fairly rare.


Sewage and polluted water, contaminated meat and milk.

Where do you find it?

Waterborne infection, faeces, unwashed fruit and vegetables, raw shellfish, raw milk and products. The majority of typhoid illnesses are acquired from endemic areas abroad.

Onset period and symptoms

The onset period for Typhoid is between 3 days and 1 month. Symptoms include fever, severe headache, nausea, loss of appetite, slow pulse, spots on the trunk and constipation.

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About the author David Lee David has worked with the CPD Online College from the start.

He works on the website by making sure our courses are easy to use and packed full of useful information. Outside of work he enjoys time with friends and family, walking his dog Molly and eating Nutella by the jar full. And Jaffa Cakes. And basically anything else he can get his hands on.

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