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FOOD POISONING - a patient's guide
Editorial Team
Overview
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:
Chicken
Eggs
Ready to eat foods (i.e. processed meat, soft cheese)
Shellfish
Unpasteurised milk
Untreated water
Common foodborne illnesses:
Salmonella
Campylobacter
E.coli
Bacterial gastroenteritis
Shigella
Listeria
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 & signs:
- A cluster of food poisoning in people who ate the same food
- Fever and chills
- Weakness
- Headache
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.
Prevention
Most cases of food poisoning can be prevented by using hygienic food
handling practises and ensuring food is cooked thoroughly. See article
on food safety for detailed information about safe food storage, and handling.
Types of food poisoning:
Salmonella
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.
Campylobacter
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.
E.coli
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.
Staphlycoccus 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.
Listeria
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.
Getting help
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.
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