There are two types of food illness:

• Food poisoning, which is triggered by eating contaminated foods caused by harmful substances or harmful bacteria.
• Food-borne diseases caused by food or water carrying harmful micro-organisms.

Food poisoning

Food poisoning is a preventable illness, usually of sudden onset, brought about by eating harmful substances or bacteria living on the food. Symptoms usually starts fairly soon after eating the contaminated food and lasts for 24-48 hours but can continue for a week or so. The illness is recognised by one or more of the following symptoms: diarrhoea, abdominal pain, vomiting and nausea.

Food-borne diseases

Many diseases are transferred to humans by micro-organisms which are carried by food or water. Campylobacter and escherichia coli are common food borne diseases. Only a few micro-organisms are needed to give you a food borne disease. The incubation period can vary to a few days, weeks or months with the illness lasting a few days or even for years where it invades the bloodstream causing long term health problems.

Below is a list of common food borne illnesses, their symptoms, mode of transmission and preventable methods.

Bacillus cereus

What is it?

Bacillus cereus spores survive normal cooking and can multiply rapidly in food. It grows between 7^oC and 48^oC with an optimum temperature between 28^oC and 35^oC. It is distributed throughout the environment but is particularly common in soil, vegetation, cereals and spices.

How is it spread?

The spread can occur through contaminated cooked foods, especially rice and pasta dishes subjected to inadequate temperature controls during cooking and storage.

What are the symptoms?

The symptoms are nausea, vomiting, abdominal pains and diarrhoea.

What can you do to avoid it?

The control method is effective temperature control to minimise the growth of spores. Cooked foods should be held hot (>60^oC) before consumption or stored at refrigeration temperature for a carefully limited time.

Campylobacter

What is it?

Campylobacter are a family of bacteria. They are one of the commonest causes of diarrhoea in animals and man. After the bacteria have been swallowed, they multiply in the gut and produce symptoms between 1 and 7 days later. Campylobacter infection is characterised by severely cramping abdominal pains, fever and diarrhoea. Vomiting rarely occurs. These symptoms are produced by the body in an effort to "flush out the system". The illness is usually over within 10 days.

How is it spread?

Studies have shown that campylobacter can be isolated from a wide variety of sources including chicken and other birds, cattle, goats and pond and river water. It has been found that it only needs a few bacteria to give rise to infection compared with many thousands required for organisms like salmonella to cause food poisoning. With such a small infective dose it might be reasonably expected that campylobacter would spread easily from person to person. However, this is not the case and such transmission is the exception rather than the rule. The reason for this is that campylobacter do not survive very long outside the body (human or animal). This applies even if they are allowed to contaminate foodstuffs. The main exception is milk in which they can survive for some weeks.

Large outbreaks are uncommon but when they do occur they are often due to consumption of either unpasteurised (or adequately pasteurised) milk or treated milk that has subsequently become contaminated. In the latter case, recent evidence has shown that the pecking of bottles of doorstep-delivered milk y birds of the crow family (jackdaws, magpies etc.) has led to cases of campylobacter infection

How do you catch it and what can you do to avoid it?

Apart from the problems with unpasteurised milk outlined above, the other main sources to be aware of are raw meats and poultry and infected pets.

Since various animals are carriers of campylobacter, raw meat obtained from those animals is likely to be a source of infection. Poultry meat in particular should be well cooked until the juices run clear to avoid the likelihood of campylobacter infection (as well as food poisoning from other bacteria such as salmonella). The increased use of barbecues has led to campylobacter being labelled "the barbecue bug" since it often happens that meat is inadequately cooked on barbecues with disastrous consequences!

Also, do not allow raw meat or poultry to come into contact with other foods. Use a separate knife and chopping board for raw meats and poultry.

Around 50% of dogs and cats excrete the campylobacter bacteria in their faeces; this is particularly a problem in young animals. As a result their coats become contaminated allowing the bacteria to be passed on to humans, especially children who stroke the animals. It if therefore important to ensure that pet's bedding and feeding bowls are kept clean and disinfected. In addition you should never wash your pets feeding bowls with family dishes or allow pets to lick from family dinner plates.

What is the treatment?

If you have diarrhoea then drink plenty of fluids. Antibiotics are not usually helpful in campylobacter, although if you are extremely poorly your doctor may give them.

What should you do to prevent further spread?

Pay particular attention to personal hygiene: hands should be thoroughly washed (using hot water, soap and a nail brush) after using the toilet and immediately prior to any handling, preparation or serving of food. Towels should not be shared. Children should be supervised in their hand washing after using the toilet and before eating food.

Soiled clothing and bed linen should be washed in a domestic washing machine with a hot cycle. As much faecal material as possible should be disposed of down the toilet if linen has become heavily soiled. Soaking in a household disinfectant before washing may also be used to reduce the contamination. Disposable plastic or rubber gloves should also be worn and hands thoroughly washed afterwards.

Clean toilet seats, flush handles, door handles and taps frequently with hot soapy water. You do not need to use disinfectants, but if you want to then follow the manufacturer instructions carefully, and keep them away from children.

When can you go back to work/school?

You should stay away from work or school until you have been free from diarrhoea for at least 48 hours. [From an information leaflet published by Nottingham and North Nottinghamshire Health Authorities]

Clostridium perfringens

What is it?

These spores survive normal cooking and may be stimulated to germinate. Spore multiplication occurs if subsequent temperature control in inadequate.

The source emanates from the faeces of animals and man, soil, sewage, dust and feeds of animal origin.

How do you catch it?

The spread can occur from contaminated bulk cooked meat and poultry dishes which have been left at ambient temperature after cooking, during cooling and storage.

What are the symptoms?

The symptoms are diarrhoea and acute abdominal pain; vomiting is uncommon. Complications and death are rare and usually occur only in elderly/debilitated people. The onset period is between 8-18 hours.

What can I do to avoid it?

To prevent the occurrence ensure raw and cooked foods are separated and good hygiene practices are maintained together with adequate thorough cooking.

Dysentery

What is it?

Dysentery is an infection of the digestive system caused, usually, by a bacterium called shigella. It is highly infectious because the infective dose (the number of bacteria that are required to produce illness) is very low. Anyone can become infected although it is most common in children aged under 10 years.

The incubation period can be anywhere between 10 hours to 7 days, usually 2 to 3 days. The majority of cases clear up after 2 to 3 days but some patients may be ill for 2 to 3 weeks. The onset is usually abrupt with fever followed by vomiting, abdominal pain and profuse diarrhoea.

How do you catch it?

The source of dysentery bacteria is the faeces (stools) of infected persons, particularly those persons who still have diarrhoea.

The infection is mainly spread by the "feacal-oral" route from person to person - in fact this disease is only a disease of man, involving hand to mouth transfer via materials and surfaces contaminated by an infected person, e.g. the person who used the toilet before you may have left bacteria on the seat, handle or door.

Some more sever forms may be caught abroad, especially in tropical countries.

How can you avoid it?

By scrupulous attention to hygiene. Always wash and dry your hands thoroughly after using the toilet and teach your children the importance of doing the same.

What is the treatment?

If you have diarrhoea then drink plenty of fluids. Antibiotics are not usually helpful in dysentery, although if you are extremely poorly your doctor may give them.

What can you do to prevent further spread?

Pay particular attention to personal hygiene: hands should be thoroughly washed (using hot water, soap and a nail brush) after using the toilet and immediately before any handling, preparing or serving of food. Towels should not be shared. Children should be supervised in their hand-washing after using the toilet and before eating food. Particular care should also be taken if you have to attend to elderly relatives suffering from diarrhoea associated with a shigella infection.

Soiled clothing and bed linen should be washed in a domestic washing machine with a hot cycle. As much faecal matter as possible should be flushed down the toilet. Soaking in a household disinfectant may also be used, before washing, to reduce contamination. Disposable plastic or rubber gloves should be worn and hands thoroughly washed afterwards.

Clean toilet seats, flush handles, door handles and taps frequently with hot soapy water. You do not need to use disinfectants, but if you want to then follow the manufacturer's instructions carefully, and keep them away from children. Shigella bacteria are quite hardy and can remain on such objects for some time, capable of being picked up on the hands of any person and then transferred to their mouth.

When can you go back to work/school?

You should stay away from work or school until you have been free from diarrhoea and vomiting for at least 48 hours. The environmental health department may tell you to stay off longer or may ask for further faeces specimens, especially if you work in food preparation, child care etc. You must follow their advice. [From an information leaflet published by Nottingham and North Nottinghamshire Health Authorities]

Escherichia coli 0157

What is it?

Veroctytoxin producing escherichia coli (VTEC) are bacteria responsible for a range of illnesses in humans from mild diarrhoea to severe colitis, renal failure and septic shock. There are a number of different types of VTEC bacteria, the most common responsible for human diseases in the United Kingdom being escherichia coli 0157. Numbers of cases have risen steadily from less than 10 each year in the early 1980s to 1039 in 1995. At present most of these infections are diagnosed in children under 5 years of age and the majority of cases occur in the Autumn.

How do you catch it?

Usually by eating food or drink contaminated with escherichia coli 0157. Cattle are thought to be the main reservoir of infection and several large outbreaks have occurred in the United States that have been associated with eating undercooked beef burgers. Other suggested sources include contaminated milk and yoghurt, faecally contaminated raw vegetables and water and cooked meats. Spread of the infection from person to person has occurred within households, nurseries and infant schools, nursing and residential homes.

Direct contact with animals, particularly on farms or in animal sanctuaries, has also been reported as a source.

Only small numbers of bacteria, e.g. less than 10 organisms, are necessary to cause illness.

How can you avoid it?

Exposure to VTEC bacteria can be significantly reduced by cooking beef burgers, and other meats, thoroughly until the juices run clear and there are no pink areas inside. Vulnerable groups such as children, the elderly and immunocompromised patients should also avoid the consumption of unpasteurised milk. If visiting farms animals sanctuaries etc. hands should be thoroughly washed after touching/feeding any of the animals and especially before eating any food.

What symptoms does it cause?

Diarrhoea is the commonest symptom and it may be a self-limiting mild diarrhoea that settles within two weeks but it can progress to a more serious colitis with severe abdominal pain and bloody diarrhoea. A very small proportion of cases go on to develop the haemolytic uraemic syndrome, which is a type o renal failure associated with anaemia and other blood disorders. This syndrome, which can on very rare occasions leads to death, is a more likely complication of VTEC infections in children and, to a lesser extent, the elderly.

What is the treatment?

As these infections are usually self-limiting, only simple measures such as plenty of fluids, a light diet and rest are needed. If more serious complications develop, then these are treated in hospital.

Is there anything else you should do while you are ill?

• Avoid contact with other people until your diarrhoea has stopped, especially children and vulnerable people.
• Avoid preparing food for other people.
• Make sure everyone at home has their own towel.
• Clean toilet seats, flush handles, door handles and taps frequently with hot soapy water.
• You do not need to use disinfectants, but if you want to then follow the manufacturer instructions carefully, and keep them away from children.
• Soiled clothes should be laundered on as hot a wash as possible.

When can you return to work/school?

You will be contacted by an Environmental Health Officer from your Local authority to see if they can identify where you may have contracted the disease. The Environmental Health Officer will tell you how long to stay off. In general you will be told to remain off work/school until you have been free from diarrhoea and vomiting for at least 48 hours. If there might be special risks of the infection spreading further, you will be given additional advice.

Those that do pose a special risk of spreading infection, i.e. children under 5 years of age, food handlers or health care worker, will be told to remain off work/school until two consecutive faecal specimens, taken at 48 hour intervals, have been found to be clear of the organism.

[From an information leaflet published by Nottingham and North Nottinghamshire Health Authorities]

Giardiasis

What is it?

Giardia is a very small parasite (known as protozoan) invisible to the human eye. Once swallowed, the characteristic symptom is diarrhoea, which may be profuse, watery and foul smelling, often accompanied by nausea (feeling sick) and abdominal pain, but many of those infected may in fact show few symptom. The incubation period can vary anywhere between 5 to 25 days, usually 7 to 10 days (in the UK children are more frequently infected than adults).

How do you catch it?

Giardia is spread by the "faecal oral" route either by direct person-to-person contact (in fact this is only a disease of man) involving hand to mouth transfer from contaminated materials and surfaces, or indirectly through eating food which has become contaminated in the same way. Transmission of the infection can also occur in areas of poor sanitation where water supplies have become contaminated with human sewage.

Infection is also commonly associated with foreign travel.

How can you prevent spread?

Pay particular attention to personal hygiene. Thorough hand washing (using hot soapy water and a nail brush) each time after using the toilet and immediately prior to any handling, preparation or serving of food. Towels must not be shared. Children must be supervised to thoroughly wash their hands after using the toilet and before eating food.

Soiled clothing and bed linen should be washed in a domestic washing machine with a hot cycle. As much faecal matter as possible should be flushed down the toilet. Soaking in a household disinfectant may also be used, before washing, to reduce contamination. Disposable plastic or rubber gloves should be worn and hands thoroughly washed afterwards.

Clean toilet seats, flush handles, door handles and taps frequently with hot soapy water. You do not need to use disinfectants, but if you want to then follow the manufacturer's instructions carefully, and keep them away from children.

When can I return to work/school?

You should stay away from work or school until you have been free from diarrhoea and vomiting for at least 48 hours.

[From an information leaflet published by Nottingham and North Nottinghamshire Health Authorities]

Listeria

What is it?

The illness is known as listeriosis. Although food is not the only means of transmission, listeriosis may be considered as a food borne illness and is caused by listeria monocytogenes.

How do you catch it?

The bacteria may be excreted by human or animal carriers and many cases of cross contamination have been recorded. The bacterium has been isolated from a range of raw foods including vegetables and uncooked meats as well as processed foods. a wide range of food products have been implicated in outbreaks including soft cheeses and meat based pates.

What are the symptoms?

Symptoms can be flu-like or more serious such as fever, septicemia, meningitis and abortion; neonates, pregnant women and immuno-suppressed persons and the elderly are most at risk. the incubation period is one to 70 days.

How can you avoid it?

Pregnant women and immuno-compromised persons should avoid eating certain ripened soft cheeses such as camembert, brie, blue veined varieties and some types of meat based pate. Cook-chill meals and ready to eat poultry should be heated until they are piping hot. Pregnant women should not help with lambing, milk ewes that have recently given birth, touch the afterbirth or come into contact with new born lambs.

Salmonella

What is it?

It is an illness caused by salmonella bacteria. The bacteria are swallowed, usually in food, and then multiply in the gut. After 12 to 36 hours (called the incubation period) symptoms develop in the infected person. Salmonella infection is characterised by vomiting, diarrhoea, abdominal pain, sometimes with an associated fever and general malaise (feeling unwell). This may continue for 2 to 3 days followed by gradual recovery. In the very young or elderly, or people with a weakened immune system, the symptoms may be more sever, last longer and they may take longer to recover.

How do you catch it?

Usually by eating food or drink that is contaminated by the bacteria. Salmonella is more common in some foods, such raw poultry, unpasteurised (green top) milk, and raw eggs. It may also be found in shellfish and many other foods. You can also catch it from someone who is ill with salmonella, especially if hygiene is poor.

How can you avoid it?

• Always cook poultry thoroughly until the juices run clear. Make sure that frozen turkeys, chickens, etc. are properly defrosted before you cook them. If possible always defrost them in the bottom of the fridge.
• Do not eat dishes made with raw eggs, i.e. some home made mayonnaise, cheesecakes and desserts.
• Do not serve eggs with runny yolks to the elderly, very young and those who are recovering from other illnesses.
• Do not drink unpasteurised (green top) milk.
• Do not allow raw meat or poultry to come into contact with other foods. Use a separate knife and chopping board for raw meats and poultry.
• Store food at the right temperature so that the bacteria cannot multiply. Either keep it cold (below 5^oC) or hot (above 63^oC).
• Always wash and dry your hands after using the toilet and before preparing food.

What can you do to prevent further spread?

Pay particular attention to personal hygiene: hands should be thoroughly washed (using hot water, soap and a nail brush) after using the toilet and immediately before any handling, preparing or serving of food. Towels should not be shared. Children should be supervised in their hand-washing after using the toilet and before eating food. Particular care should also betaken if you have to attend to elderly relatives suffering from diarrhoea associated with a salmonella infection.

Soiled clothing and bed linen should be washed in a domestic washing machine with a hot cycle. As much faecal matter as possible should be flushed down the toilet. Soaking in a household disinfectant may also be used before washing, to reduce contamination. Disposable plastic or rubber gloves should be worn and hands thoroughly washed afterwards.

Clean toilet seat, flush handles and taps frequently with hot soapy water. You do not need to use disinfectants, but if you want to then follow the manufacturer's instructions carefully, and keep them away from children.

When can you go back to work/school?

You should stay away from work or school until you have been free from he diarrhoea and vomiting for at least 48 hours. The Environmental Health Department may tell you to stay off longer or may ask for further faeces specimens. You must follow their advice.

[From an information leaflet published by Nottingham and North Nottinghamshire Health Authorities]

Staphylococcus aureus

What is it?

Staphylococcal food poisoning has become less common since its peak in the 1950s when there were approximately 150 outbreaks per year, declining to about 13 outbreaks a year in England and Wales between 1969 and 1990. It is the main bacterial type of food poisoning that arises from human contamination of food rather than originating from the food itself or other environmental source.

How does it spread?

Human contamination. Staphylococcus aureus causes skin and wound infections and is carried in the nose of 40% of healthy people and commonly also in the gut.

Foods most often associated are cooked meats, poultry and foods which are handling during preparation without further heating before consumption.

What are the symptoms?

Vomiting, abdominal cramps and diarrhoea. The illness may be so acute that sufferers faint or collapse and may require rehydrating.

How can I avoid it?

Reduce food handling time to a minimum and keep food hot >63^oC and cold <4^oC and cover in storage if necessary.

Sources:

• Sprenger, Richard A., "Hygiene for Management" (Highfield Publications, 1995).
• Department of Health Working Group, "Managment of Outbreaks of Foodborne Illness" (Department of Health, 1994)