Causes of food poisoning
We investigate certain infectious diseases, food poisoning and other food-borne illnesses that are notified to Public Health England. The aim is to try to prevent the spread of illness and establish possible causes.
Many different sorts of bacteria, or germs, can cause food poisoning. When food is kept at the wrong temperature, these bacteria can grow rapidly and reach dangerous levels within hours.
The incubation period, that's the time taken from eating the food to feeling unwell, varies but in most cases is one to three days after eating the food. The last meal you ate may not be the cause of your symptoms.
The main causes of food poisoning are:
- Preparing foods too far in advance
- Not cooking foods thoroughly
- Not defrosting foods correctly
- Storing foods incorrectly so that bacteria can grow quickly
- Cross-contamination of foods after cooking
- Poor personal hygiene of people handling the food
We're all at risk but babies, young children and the elderly can become very ill when infected. Pregnant women, people who already have a pre-existing illness and anyone whose immune system is weakened can also be seriously affected by food poisoning.
Symptoms of food poisoning
The main symptoms are:
- Stomach cramps
There are many types of food poisoning caused by different bacteria. The most common include:
Symptoms include stomach cramps and severe diarrhoea but rarely vomiting. They can begin two to ten days after eating contaminated food but usually within three to five days. Main sources are raw or undercooked chicken and other meats, handling pets, cross-contamination, raw milk and contaminated water.
Symptoms include stomach cramps, fever, diarrhoea and vomiting. It usually takes about 12 to 48 hours for the illness to develop. Symptoms can be much more severe in the young and elderly. Main sources are raw or undercooked meat and poultry, untreated milk, handling pets (particularly reptiles), cross-contamination and raw or undercooked eggs (please note the current advice is that Lion stamped hens eggs can be eaten raw or lightly cooked).
Symptoms include diarrhoea which can be severe and/or bloody, and the infection can lead to serious kidney damage in children. Main sources are undercooked beefburgers and minced beef, cross-contamination and unpasteurised milk. This organism has also been linked to farms.
Symptoms include stomach cramps and vomiting, one to six hours after eating and it usually takes 12 to 24 hours for symptoms to subside. This bacteria is found naturally on humans, particularly in the nose, throat, skin and ears, and is transferred to food through poor hygiene practices.
Symptoms include mild flu-like illness in healthy people, but can cause septicaemia and meningitis in the young and elderly. Listeria can lead to stillbirth and miscarriage or meningitis in the new-born baby. Sources include unpasteurised soft cheeses, such as brie and camembert, and meat pates; pregnant women are advised not to eat them. Prevention of food poisoning from Listeria is more difficult than other organisms as it can multiply at refrigeration temperatures.
- Wash hands thoroughly before handling food and always after handling raw meat or unwashed vegetables, going to the toilet, blowing your nose or handling animals, including pets
- Keep food preparation surfaces and utensils clean and disinfected
- Prepare and store raw meat and “ready-to-eat” food separately. Always keep raw and defrosting meat at the base of the refrigerator, below everything else
- Ensure that your refrigerator and freezer are operating properly and invest in a suitable thermometer. The refrigerator should operate at five degrees centigrade or lower and the freezer at -18 degrees centigrade or lower
- Check the use by dates on food and ensure that you use the food before the date expires
- Always store eggs in the refrigerator
- Keep pets away from food and food preparation surfaces
- Defrost food, particularly meat and poultry, thoroughly before cooking
- Cook food thoroughly; follow the instructions on the packaging where provided
- Cool food immediately after cooking and never allow it to be at room temperature for more than four hours. Always store left-over food in the refrigerator as soon as it's cooled to room temperature
What to do if you have symptoms
If you suspect you're suffering from food poisoning, visit your doctor as soon as possible. You may be asked to submit a sample for examination. This is to find out what is causing your illness. This is important as it is not just food poisoning bacteria which can cause these symptoms and this information can be used in our investigation.
Consult your doctor immediately if the person affected is a baby, elderly or has an existing illness or condition or if symptoms are prolonged or severe, such as bloody diarrhoea.
If you or a member of your family are suffering from food poisoning symptoms:
- Wash your hands after contact with the sick person, and before handling food
- Don't use the same towel or face cloth as someone who is suffering with food poisoning
- Clear up soiling accidents straight away, wash with hot soapy water and disinfect with a disinfectant or bleach
- Disinfect door and toilet handles, taps and the toilet seat after use and disinfect the toilet bowl frequently
- Drink plenty of fluids while you are ill to prevent dehydration