AN OVERVIEW OF FOOD POISONING - a patient's guide
- Food poisoning is relatively common, especially during the summer months
- There are several different types of food poisoning such as campylobacter, salmonella, E.coli and staph aureus food poisoning
- Symptoms include diarrhoea, stomach cramps, nausea, and vomiting
- Treatment involves replacing lost fluids with water and electrolyte solutions. Antispasmodic medications are used to relieve stomach cramps in some cases
- Dehydration or severe vomiting may require hospitalisation
What is it?
Food poisoning refers to any illness caused by eating contaminated food. The food may contain toxins produced by staphylococcal organisms, bacteria such as E.coli and salmonella, botulism, and other poisons.
Food poisoning remains a fairly common illness affecting about one in three people each year. It is particularly prevalent in the summer months when foods have been left out of the fridge for some time.
Most people have experienced food poisoning at some time and it can occur in both restaurants and in the home. However, careful hygiene and food handling practises can prevent most cases of food poisoning.
The mass production of food has increased the opportunity for food poisons to infect large populations. It is now possible for food to become contaminated in one country and cause outbreaks of food poisoning in another.
The US National Food and Safety initiative attributes 9000 deaths and between 6.5 million and 33 million cases of food poisoning annually to food poisoning. It is believed there are 9.4 million cases of gastrointestinal illness in England annually.
Foods commonly associated with food poisoning:
- Ready to eat foods (i.e. processed meat, soft cheese)
- Unpasteurised milk
- Untreated water
Common foodborne illnesses:
- Bacterial gastroenteritis
- Staph aureus food poisoning
What are the symptoms?
Classical food poisoning with staphylococcal organisms usually appears within three hours of eating the contaminated food. The illness normally begins with nausea, leading to severe vomiting.
Other types of food poisoning such as campylobacter may only cause diarrhoea and abdominal cramps, without vomiting, although vomiting can occur in some cases.
Some forms of food poisoning have an incubation period of up to several days so it can be hard to identify the source of contamination.
Other possible symptoms:
- A cluster of food poisoning in people who ate the same food
- Fever and chills
Examining the suspected food for any poison or bacteria can confirm the diagnosis. A diagnosis can also be made by testing stool or vomit samples.
The illness will normally last about a day, although many people can still feel weak and off colour for several days afterwards.
What can be done to help?
Treatment involves measures to avoid dehydration. Drink plenty of water and electrolyte solutions to replace lost salt and minerals.
Avoid dairy products during the illness. Eat bland foods such as bananas, apples, and unbuttered toast. Babies should continue to be breastfed and given electrolyte solutions.
Those suffering from stomach cramps may get relief from taking an antispasmodic medicine. Anti-diarrhoea medications are generally not given because they may prolong the infection.
People taking diuretic medication should ask their doctor whether to keep taking them while they have diarrhoea. In some cases they may need to be stopped during the acute phase of the illness.
People who are unable to keep anything down due to nausea may need medication to stop them vomiting, and require intravenous feeding in some cases.
Most cases of food poisoning can be prevented by using hygienic food handling practises and ensuring food is cooked thoroughly. See FamilyDoctor article on food safety for detailed information about safe food storage, and handling.
Types of food poisoning
Salmonella enterocolitis is an illness caused by contaminated food or water, causing inflammation in the lining of the small intestine.
It can cause mild to severe diarrhoea, stomach cramps, vomiting and muscle aches and pains.
Preparing food in unsanitary conditions can lead to contamination with the bacteria.
People become ill 8 to 48 hours after exposure and the illness can last up to 2 weeks. However, most people have recovered within 2 to 5 days.
Some people can also become carriers, shedding the bacteria in stools up to one year following an infection.
The illness peaks in the summer months and other risk factors include:
- Eating undercooked poultry (chicken, turkey, and eggs)
- Eating unrefrigerated poultry
- Salmonella illness within the household
- Unsanitary cooking conditions
- Contact with turtles, lizards, snakes and other reptiles which are carriers of salmonella
Salmonella has been found in 1 percent of eggs and 20 percent of all poultry. However, it's thought thorough cooking will prevent food poisoning with salmonella.
This is one of the most common forms of food poisoning. It causes swelling in the lining of the small intestine.
A common source of infection is contaminated poultry (chicken, turkey, eggs), milk and water. Other risk factors include contact with family members who have had the illness, and travel in developing countries.
It does not usually cause vomiting. The main symptoms are watery diarrhoea, cramps and stomach pain, fever, and possible blood in stools.
The illness develops after a 2 to 4 day incubation period and usually lasts less than one week.
Treatment may involve antibiotic therapy. However, the bacteria is resistant to many antibiotics and treatment is not routinely advised.
In rare cases campylobacter can cause blood poisoning, a form of arthritis, and brain inflammation.
Food poisoning with certain strains of E.coli causes a severe gastrointestinal illness which can be life threatening in infants, children, the elderly, and those with weak immune systems.
Certain types of E.coli infection can lead to destruction of the red blood cells, a sharp drop in the platelets, and kidney failure.
The illness has an incubation period of between 24 to 72 hours and symptoms include acute diarrhoea, stomach pain, and vomiting in rare cases. Most people have recovered after three days. Seek medical help if blood in stools is noticed or new symptoms develop.
Risk factors include undercooked meats, particularly mince meat, untreated and contaminated water, contact with a person who has been ill with E.coli or gastroenteritis, and travel to an area with a high incidence of E.coli.
Outbreaks have also been linked to handling soiled potatoes, yoghurt, apple juice, and unpasteurised milk. Outbreaks are also prone among preschool children and in day care centres.
E.coli has been detected in up to 15 percent of British cattle which is worrying due to the fact that beef is often eaten undercooked or rare.
Staph aureus food poisoning:
This is a type of food poisoning from eating food contaminated with a poison produced by staph aureus bacteria.
It often occurs when food is contaminated by unhygienic food preparation such as a food handler with a skin infection, and food being stored at room temperature.
Staph aureus commonly infects food that is served cool such as creamy desserts, custards, salads, cold meats and baked foods.
Symptoms usually appear within four to six hours and include vomiting for up to 24 hours, diarrhoea, severe stomach cramps and fever.
People usually recover within 24 to 48 hours.
This illness usually causes no symptoms in the general population. However, it can be harmful to the elderly, unborn children, and those with weak immune systems.
The toxin is found in shellfish, pate, processed meats, and soft cheese. Pregnant women should avoid eating these foods because listeria can be fatal for the foetus.
Listeria causes flu-like symptoms from 4 hours to several days.
Many people do not seek medical help and make an uneventful recovery.
However, the following factors should lead to earlier consideration of seeking medical advice:
- Recent travel overseas
- Severe vomiting
- Dehydration (symptoms include dry mouth, less urine, sunken eyes)
- Severe or persisting abdominal pain
- Symptoms such as severe associated headaches
- Blood in stools or vomiting blood
- Diarrhoea persisting beyond 4-5 days, in which case most doctors would consider doing stool tests depending on the circumstances.
- The elderly are particularly at risk of dehydration and resulting kidney problems, and should seek prompt advice
- Patients on medication, particularly for heart conditions and diabetes should seek prompt and early medical advice
- Young children and babies are very susceptible to rapid and dangerous dehydration, and advice should be sought early.