Food poisoning is a common acute illness caused by eating contaminated food. Symptoms may last from a few hours to several days. Symptoms may include abdominal pain, diarrhoea, vomiting, nausea, and fever. In some cases, death may occur, particularly with the elderly. Remember that allergies are not food poisoning.

Food poisoning is caused by:

• Bacteria or bacterial toxins
• Viruses
• Chemicals (e.g. insecticides, cleaning chemicals)
• Metals (e.g. lead, mercury)
• Mycotoxins produced by moulds
• Poisonous plants and fish
• Parasites (e.g. Cryptosporidium)

The most common form of food poisoning is bacterial, but viral food poisoning is also very common.

Common food poisoning bacteria include:

Salmonella The primary source of this organism is the intestinal tract of animals and birds. Raw meat, raw poultry and raw eggs are the most common food sources. Flies and animals, including pets, can carry the organism.

Clostridium perfringens
This organism is found in soil and in animal and human excreta. It can produce spores that can survive cooking. If food is not cooled quickly and is then left out of the fridge for long periods after cooking, the organism can multiply very quickly and cause food poisoning.

Staphylococcus aureus
This organism is found in the noses of 40% of adults. It can also be found on the skin, in boils and in cuts. It can also be found in raw meat and raw milk.

Clostridium botulinum
This is the most serious form of food poisoning. The organism produces the most toxic chemical known to man. Fortunately, this type of food poisoning is very rare in the U.K. The organism is found in soil, fish, meat and vegetables.

Bacillus cereus
This is found frequently in the soil and therefore on rice, vegetation, cereals and spices. It produces spores that can survive cooking. If the food is cooled slowly and left out of the fridge after cooking, the spores germinate and grow rapidly.

Some bacteria cause food-borne infections. These are different from food poisoning bacteria in that only very small numbers of bacteria are needed to cause illness, and infection may be spread by non-food items.

Typhoid
This is a very serious illness spread by water, food and from person to person. It is uncommon in this country, but there are a number of cases each year in the U.K., usually imported from other countries.

Campylobacter
This is very common and is frequently found in raw poultry and raw milk. Bottled milk that has been pecked by birds has also caused infection. Animals and wild birds often spread the infection.

Listeria
Listeria is a problem for the food industry because it can grow, albeit slowly, at 3°C. In other words, it can grow on food in your fridge. Consumption of soft cheeses and pate has resulted in infection. The illness is particularly serious in pregnant women, where abortion can occur, and in the very young and the elderly.

E. coli 0157
E.coli 0157 is a serious food-borne illness. It is found in the intestinal tract of animals and in excreta. Raw meat and raw milk are common sources of the organism. It is a serious illness for the very young and the elderly. It can damage the kidneys in children and often kills the elderly.

Viruses
These are very unusual organisms. Some people argue that they are not strictly speaking living organisms, because they don't respire (breathe). Alive or not, they cause many cases of food-borne infection every year. They do not grow in the food. In fact they can only grow inside a living cell. Foods frequently infected are shellfish, including oysters, cockles and molluscs, which tend to concentrate viruses from sewage-polluted waters.

Other types of food poisoning:

Mycotoxins
Moulds produce mycotoxins. Long term, low level consumption can lead to cancer and cirrhosis of the liver. In underdeveloped countries, they can cause acute illness and in serious cases death. Poor storage of products such as cereals, grains and rice can lead to mould growing in the product and mycotoxin production.

Poisonous plants and fish
These rarely cause food poisoning in the U.K. but food poisoning can occur from consumption of, for example, undercooked or raw kidney beans and from consumption of poisonous fish.

Chemicals
Consumption of heavy metals, such as mercury and cadmium, can cause illness. Also some cleaning chemicals can also cause illness. Hence it is very important to rinse away cleaning chemicals before preparing food.

Parasites
These are small organisms that live on another animals. They include tapeworms, flukes, etc. Again they are relatively rare and are often associated with animals.