Food poisoning
Food can become contaminated at any stage during its production, processing or cooking.
For example,it can become contaminated by:
Cross-contamination can occur, for example, if you prepare raw chicken on a chopping board and don't wash the board before preparing food that won't be cooked (such as salad), as the harmful bacteria can be spread from the chopping board to the salad.
Itcan also occur if raw meat is stored above ready-to-eat meals and juices from the meat drip on to the food below.
See preventing food poisoning for information about reducing these risks.
Food contamination is usually caused by bacteria, but it can also sometimes be caused by viruses or parasites. Some of the main sources of contamination are described below.
In the UK, campylobacter bacteria are the most common cause of food poisoning. The bacteria are usually found on raw or undercooked meat (particularly poultry), unpasteurised milk and untreated water.
The incubation period (the time between eating contaminated food and the start of symptoms) for food poisoning caused by campylobacter is usually between two and five days. The symptoms usually last less than a week.
Salmonella bacteria are often found in raw or undercooked meat, raw eggs, milk, and other dairy products.
The incubation period is usually between 12 and 72 hours. The symptoms usually last around four to seven days.
This is particularly important for pregnant women, because a listeria infection (known as listeriosis) in pregnancy can cause pregnancy and birth complications, and can result in miscarriage .
The incubation period can vary considerably, from a few days to several weeks. The symptoms will usually pass within three days.
coli)
Escherichia coli, often known as E. coli, are bacteria found in the digestive systems of many animals, including humans. Most strains are harmless but some can cause serious illness.
Most cases of E. coli food poisoning occur after eating undercooked beef (particularly mince, burgers and meatballs) or drinking unpasteurised milk.
The incubation period for food poisoning caused by E. coli is typically one to eight days. The symptoms usually last for a few days or weeks.
Shigella bacteria cancontaminate any food that has been washed in contaminated water.
Symptoms typically develop within seven days of eating contaminated food and last for up to a week.
An infection caused by Shigella bacteria is known as bacillary dysentery or shigellosis. See the topic on dysentery for more information about it.
The virus that most commonly causes diarrhoea and vomiting is the norovirus . It's easily spread from person to person, through contaminated food or water. Raw shellfish, particularly oysters, can also be a source of infection.
The incubation period typically lasts 24-48 hours and the symptoms usually pass in a couple of days.
In young children, the rotavirus is a common cause of infection from contaminated food. The symptoms usually develop within a week and pass in around five to seven days.
In the UK, food poisoningcaused by parasites is rare. It's much more common in the developing world.
Parasitic infections that can be spread in contaminated food include:
The symptoms of food poisoning caused by a parasite usually develop within 10 days of eating contaminated food, although sometimes it may be weeks before you feel unwell.
If left untreated, the symptoms can last a long time sometimes several weeks or even a few months.
Food poisoning is an illness caused by eating contaminated food. It's not usually serious and most people get better within a few days without treatment.
Food can become contaminated at any stage during its production, processing or cooking.
Food poisoning can usually be treated at home without seeking medical advice. Most people will feel better within a few days.
The best way to avoid getting food poisoning is to ensure you maintain high standards of personal and food hygiene when storing, handling and preparing food.