1. What is food poisoning?
Food poisoning is an infection or intoxification in the human gut caused by the consumption of food or water which has been contaminated by food poisoning organisms or their toxins.
Common food poisoning organisms include:
(See below for further information about these.)
Symptoms vary from one organism to the next but commonly they will include, nausea, vomiting, diarrhoea, abdominal pain and fever.
The period of time between consumption of the contaminated food and the onset of symptoms (incubation period) also varies and can range from as little as two to four hours, up to as long as ten days.
It is well known that cases of food poisoning are grossly under-reported. The official number of notified cases in 2001 was in the region of 85,000. The true figure is more likely to have been considerably more than this.
2. I would like to know more about salmonella food poisoning.
Introduction
Salmonella food poisoning is well known and is the second most common form of food poisoning in the UK. Cases have dropped considerably in recent years because of the introduction of poultry vaccination programmes designed to reduce the incidence of salmonella in eggs. There are hundreds of different types of salmonella which aids the investigation into the source of sporadic outbreaks.
Sources
Salmonella is commonly found in uncooked poultry, pork, beef, raw eggs, unpasteurised milk and untreated water.
Salmonella has also been isolated from the faeces of both sick and apparently healthy farm and domestic animals and even people. It can also be found in reptiles and fish.
Symptoms
The most common symptoms are stomach cramps, diarrhoea, fever, nausea, and sometimes vomiting. Symptoms usually commence 12 to 36 hours after consumption of the contaminated foodstuffs. Symptoms generally last for several days and can persist for up to two weeks. It is not unknown for salmonella bacteria to remain in the gut of healthy adults for many months. This causes a potential source of continued contamination should the individual be a food handler.
Prevention
3. I would like to know more about campylobacter food poisoning.
Introduction
Campylobacter is little known but, surprisingly, it is the UK’s most common form of foodborne illness. It causes more cases of diarrhoea and abdominal pain than all the other forms of food poisoning put together, including salmonella and E.coli O157. In 2001, there were approximately 50,000 cases notified in England in Wales. Infections commonly reach a peak in June every year.
Sources
Campylobacter is a bacterium commonly found in foods such as raw or undercooked poultry, raw milk and in untreated water. The bacterium is easily passed on to other ready-to-eat foods such as salad and cooked meat by poor food handling techniques. It is at barbecues in particular when these opportunities best present themselves.
Symptoms
Most people who become ill with campylobacteriosis suffer from diarrhoea, abdominal pain and fever within one to seven days (most commonly two to three days) after exposure to the organism. The diarrhoea may be bloody and can be accompanied by nausea and vomiting. The illness typically lasts about a week.
Prevention
4. I would like to know more about E.coli O157.
Introduction
E.coli O157 is a bacterium which exists and multiplies naturally in the intestines of cattle, sheep and other animals. To humans however, it can cause a potentially fatal infection and is particularly dangerous to children and the elderly. This was highlighted in the tragic deaths of 21 people during the outbreak in Lanarkshire in November 1996. Case numbers have steadily increased over the years but compared to campylobacter and salmonella it is still an uncommon form of foodborne infection. There are now more cases associated with contact with farm animals than through the consumption of unfit food.
Sources
There are two main food sources; ground beef, eg: hamburgers and beefburgers, and unpasteurised milk. Ground or chopped beef and not beef joints/steaks are considered more of a risk because the bacteria which are normally present on the surface of the beef are mixed in to the centre. Infection can result through the consumption of meat that is not cooked thoroughly. Raw food to cooked food cross contamination and person-to-person transmission may also present a threat.
Symptoms
Initial symptoms can include diarrhoea (sometimes bloody), vomiting and abdominal pain approximately one to 14 days (usually three to four days) after eating the contaminated food. In a small percentage of cases a condition known as HUS or Haemolytic Uraemic Syndrome may develop - the symptoms of which include kidney failure.
Prevention
E.coli O157 infection can be easily prevented by following the following rules:
5. I would like to know more about listeria.
Introduction
Listeria bacteria are widely distributed in nature and is the causative organism of several forms of human disease. While it is undoubtedly food-borne it cannot be truly described as a food poisoning organism since symptoms rarely include those common to other food poisoning infections. Listeria is unusual in that it can still grow at refrigeration temperatures.
Sources
Dairy products containing unpasteurised milk such as soft cheeses, fresh cream and ice-cream. Other documented sources include meat pates, coleslaw, chicken, turkey and shellfish.
Symptoms
Septicaemia, meningitis, neo-natal infection or abortion (foetuses and newborn infants are highly susceptible). The incubation period is highly variable ranging from three to 70 days.
Prevention
Pregnant women should avoid eating unpasteurised dairy products and contact with potentially infective material such as aborted animal foetuses on farms and known infected individuals.
6. I would like to know more about botulism.
Introduction
Food-borne botulism is rare in the UK, but it is a severe disease with a high mortality rate. It is a serious paralytic illness caused by a nerve toxin that is produced by the bacterium clostridium botulinum. A single case may signal a national emergency and prompt action is essential at any time of the day or night.
Sources
The bacteria are commonly found in soil and grow best in low oxygen conditions. The bacteria form spores which allow them to survive in a dormant state until exposed to conditions that can support their growth. Commercially, past cases have been associated with underprocessed low-acid foods or foods contaminated after canning or botlling. It has also been associated with home-canned foods such as asparagus, green beans, beets and corn. However, outbreaks of botulism from more unusual sources such as chopped garlic in oil, chilli peppers, tomatoes, improperly handled baked potatoes wrapped in aluminium foil, and home-canned or fermented fish have also been known.
Symptoms
The classic symptoms of botulism include double vision, blurred vision, drooping eyelids, slurred speech, difficulty swallowing, dry mouth, and muscle weakness. These are all symptoms of the muscle paralysis caused by the bacterial toxin. If untreated, these symptoms may progress to cause paralysis of the arms, legs, trunk, respiratory muscles and ultimately death.
In foodborne botulism, symptoms generally begin 18 to 36 hours after eating a contaminated food, but they can occur as early as six hours or as late as ten days.
Prevention
Botulism can be prevented. Persons who do home canning should follow strict hygienic procedures to reduce contamination of foods. Oils infused with garlic or herbs should be refrigerated. Potatoes which have been baked while wrapped in aluminium foil should be kept hot until served or refrigerated. Because the botulism toxin is destroyed by high temperatures, people who eat home-canned foods should consider boiling the food for ten minutes before eating it to ensure safety.
7. I would like to know more about bacillus cereus food poisoning.
Introduction
Bacillus cereus food poisoning is a relatively uncommon form of food poisoning but can produce some quite severe symptoms. As it is widely distributed in nature, its incidence is almost entirely due to poor temperature control of sensitive foods and so can be easily prevented.
Sources
Bacillus cereus is commonly found in soil, milk, cereals, starches, herbs, spices, and other dried food stuffs. Foods most often implicated in outbreaks include rice, meat pies and puddings.
Symptoms
Bacillus cereus can cause two distinct types of illness:
Prevention
Since Bacillus cereus bacteria are common and widespread, preventing the contamination of food with spores is virtually impossible. Consequently, effective prevention and control depends on inhibiting spore germination. This can be achieved by cooling the food rapidly after cooking to refrigeration temperatures within 90 minutes. The food should then be stored at less than 8°C and eaten within 24 hours.
8. I would like to know more about clostridium perfringens food poisoning.
Introduction
Clostridium perfringens causes an acute form of food poisoning characterised by the sudden onset of colic and diarrhoea. Cases are almost entirely due to the poor temperature control of sensitive foods following cooking and so can be easily prevented by correct food handling techniques.
Sources
Clostridium perfringens bacteria are commonly found in soil and in the intestines of healthy persons and animals. Food sources include inadequately heated or re-heated meats, stews, meat pies, and gravies made of beef, turkey or chicken.
Symptoms
Predominently abdominal pain and diarrhoea approximately six to 24 hours (usually ten to 12 hours) after eating the contaminated food.
Prevention
Serve meat dishes hot, as soon as they are cooked or cool them rapidly and refrigerate below 8°C until serving time. To achieve more rapid cooling of cooked foods divide stews and similar dishes prepared in bulk into many shallow containers.
9. I am a food handler with food poisoning. When can I return to work?
If you are employed as a food handler you must first ensure that your superviser/manager has been informed. On no account should you return to work while still unwell. You can return to work after a 48 hour symptom-free period. You must exercise normal strict personal hygiene rules whilst handling food. Most importantly make sure that you wash your hands thoroughly after visiting the toilet.
10. I would like to know more about legionnaires disease.
Introduction
Legionnaires' disease is an uncommon form of pneumonia that may have serious consequences for some people, especially people in the older age groups
Sources
The bacteria live naturally in environmental water sources but if they get into water systems in buildings they can cause a risk to humans through air conditioning systems or through contaminated water systems used for showers etc.
Symptoms
People become infected when they breathe in air that contains legionella bacteria which have been dispersed into the air in very fine droplets of water known as aerosols. If the bacteria get inhaled into the lungs they can cause infection. The early symptoms of legionellosis include a 'flu-like' illness with muscle aches, tiredness, headaches, dry cough and fever. Sometimes diarrhoea occurs and confusion may develop. These symptoms frequently lead on to pneumonia. Deaths occur in 10-15% of otherwise healthy individuals and may be higher in some groups of patients. The incubation period ranges from two to ten days but is usually three to six days. In rare cases some people may develop symptoms as late as three weeks after exposure.
Prevention
Control and prevention of the disease is through treatment of the source of infection ie: the contaminated water systems.
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