Food Poisoning

Each year it is estimated that as many as 5.5 million people in the UK may suffer from food borne illnesses €“ that€™s 1 in 10 people.

 

About germs

Germs are invisible except under a powerful microscope; hence the name micro-organisms or microbes. Microbes can be grouped according to their different structures; two common groups of microbes are viruses and bacteria.

Not all bacteria are harmful €“ indeed many are essential for life. The bacteria, viruses and other microbes that cause illness are commonly known as €˜germs€™. Germs found in food can lead to food poisoning which can be dangerous and can kill €“ though this is rare. They are very hard to detect since they do not usually affect the taste, appearance or smell of food.

The most serious types of food poisoning are due to bacteria. The more bacteria present, the more likely you are to become ill. Bacteria multiply fast and to do so need moisture, food, warmth and time. The presence or absence of oxygen, salt, sugar and the acidity of the surroundings are also important factors.

In the right conditions one bacterium can multiply to more than 4 million in just 8 hours. They multiply best between 5 and 63 degrees C but are killed at temperatures of 70 degrees C. At temperatures below 5 degrees C, most bacteria multiply very slowly, if at all. At very low temperatures some bacteria will die, but many survive and can start to multiply again if warm conditions return. This is why proper cooking and chilling of food can help reduce the risk of food poisoning.

Germs can get into our food at any point in the food chain €“ from the time when an animal or food is in the field to the moment food is put on to the table to eat. If they are allowed to survive and multiply, they can cause illness when that food is eaten.

Sometimes these germs are spread to other foods, for example via hands, or kitchen utensils and cause illness when those foods are eaten. This is known as cross-contamination.

The symptoms of food poisoning can last for days and include abdominal pains, diarrhoea, vomiting, nausea and fever. The symptoms usually come on suddenly, but can occur several days after eating contaminated food.

Food poisoning outbreaks

Sometimes groups of people can be infected at the same time. They may have eaten at a party or restaurant or there may be a batch of contaminated food being sold in different places. In such cases Environmental Health Officers (EHOs), who are employed by Local Authorities, will usually investigate the matter to find out the cause. EHOs will alert others to the dangers, offer advice, and where necessary prosecute offenders for breaches of food safety laws. Whenever such outbreaks of food poisoning occur or are suspected, it is important to contact an EHO; they can be found in the local council section of the phone book.

Seeking advice

EHOs are also happy to provide advice on food safety to local businesses. Another source of advice is the Food Standards Agency; their website address is €˜www.food.gov.uk€™.

Vulnerable groups

Food poisoning is more likely to affect people with lowered resistance to disease than healthy people who might show mild symptoms or none at all. Elderly or sick people, babies, young children and pregnant women are particularly vulnerable to food poisoning. Seek treatment if they have symptoms. Extra care should also be taken when preparing food for, and looking after, these vulnerable groups to minimise the risks of their coming into contact with food poisoning bacteria.

Avoiding food poisoning

Most food poisoning is preventable although it isn€™t possible to completely eliminate the risk.

CAMPYLOBACTER

Campylobacter can be found in raw poultry and meat, unpasteurised milk, and untreated water. Pasteurised milk can be contaminated by birds pecking bottle tops on the doorstep. Pets with diarrhoea can also be a source of infection. Campylobacter is the most common identified cause of food poisoning. Characteristics: Illness may be caused by a small number of bacteria. Cross-contamination can lead to illness. Thorough cooking and pasteurisation of milk will destroy Campylobacter.

Symptoms: Symptoms include fever, headache and a feeling of being unwell, followed by severe abdominal pain and diarrhoea which may be bloody. Symptoms normally take 2-5 days to appear but it can be as long as 10 days and return over a number of weeks.

 

 SALMONELLA

 Salmonella has been found in raw meat, poultry and eggs, raw unwashed vegetables, unpasteurised milk and dairy products and many other types of food. It is found in the gut and faeces of animals and humans. Salmonella is the second most common cause of food poisoning.

Characteristics: Salmonella survives when refrigerated although it is unable to multiply through cooking and pasteurisation. Usually large numbers of the bacteria are needed to cause infection but outbreaks have been reported where infection has been caused by a low number of bacteria.

Symptoms: It normally takes 12 to 48 hours for symptoms to develop. Symptoms may include fever, diarrhoea, vomiting and abdominal pain. Infection may be very severe, and in some cases may be fatal. It is particularly likely to cause severe illness in the very young and very old. Symptoms may last up to three weeks and there may be complications such as reactive arthritis.

E. COLI

E. coli is a widespread organism that is normally found in the guts of animals and humans. There are many different types, some of which are capable of causing illness. One uncommon type which can cause serious illness is Verocytotoxin producing E. coli O157 which has been found in raw and undercooked meats, unpasteurised milk and dairy products, raw vegetables and unpasteurised apple juice.

Characteristics: Illness may be caused by a small number of bacteria, so cross-contamination can lead to illness. The bacteria can survive refrigeration and freezer storage, but thorough cooking of food and pasteurisation of milk will kill them.

Symptoms: Symptoms normally take about 2 days to develop but may start within a day, or take up to 5 days to come on. The main symptom is diarrhoea. In some cases, particularly in children under the age of 6 and in the elderly, infection can lead to diarrhoea which may be bloody and severe, kidney failure, and sometimes death.

CLOSTRIDIUM PERFRINGENS

 Clostridium perfringens is excreted by a wide range of animals. It can be found in soil, animal manure, and sewage, and also in raw meat and poultry.

Characteristics: Clostridium perfringens produces spores which may not be killed during cooking. If foods are allowed to cool slowly, the spores germinate and produce bacteria which grow rapidly. These bacteria may not be killed if the food is not reheated until it is piping hot. It is particularly associated with gravies, cooked meat dishes, stews and pies and very large joints of meat and poultry.

Symptoms: Symptoms are mainly abdominal pain, diarrhoea and sometimes nausea starting usually 8-18 hours after eating the food. It may be fatal in the elderly and debilitated.

LISTERIA

 Source: Listeria is widely present in the environment. It is found in soil, vegetation, raw milk, meat, poultry, cheeses (particularly soft mould-ripened varieties) and salad vegetables. It is also found in the guts of animals and humans. One type, Listeria monocytogenes, can cause illness in humans.

Characteristics: Listeria monocytogenes, unlike most other food poisoning bacteria, can grow at low temperatures, even in the fridge. Thorough cooking of food and pasteurisation of milk will destroy Listeria.

Symptoms: It can take days or weeks for symptoms to develop. Symptoms can range from mild flu-like illness to meningitis and septicaemia; and in pregnant women, abortion, miscarriage or birth of an infected child. Other susceptible groups are those whose immune systems are compromised, the very young and the very old. People in these groups are advised to avoid certain foods, such as soft mould-ripened cheeses and pâtés, because of the risk of severe infection.

BACILLUS CEREUS

 Bacillus cereus is found in soil and dust. It is frequently found in rice dishes, occasionally pasta, meat or vegetable dishes, dairy products, soups, sauces and sweet pastry products where these have not been cooled quickly and effectively after cooking and during storage.

Characteristics: Illness may be caused by a small number of bacteria, so cross-contamination can lead to illness. The bacteria can form spores; they are not easily destroyed by heat and will survive cooking of food. If food is cooled slowly or kept warm for some time before serving, the spores will germinate and produce bacteria. Bacteria can multiply rapidly at these temperatures and produce a very heat resistant toxin which will not be destroyed by subsequent reheating.

Symptoms: Bacillus cereus can cause two distinct types of illness – a diarrhoeal form (diarrhoea and abdominal pain) with an incubation period of 8 to 16 hours and an emetic form (primarily vomiting, possibly with diarrhoea) with an incubation period of 1 to 5 hours. In both types the illness usually lasts less than 24 hours after onset.

STAPHYLOCOCCUS AUREUS

 Staphylococcus aureus may be found on the skin, in infected cuts and boils and in the nose. It may also be found in unpasteurised milk. It can be transferred to food from the hands or from droplets from the nose or mouth.

Characteristics: Food poisoning from Staphylococcus aureus follows the consumption of heavily contaminated food, where bacteria have multiplied and produced a toxin which causes illness when the food is consumed. Staphylococcus aureus survives when refrigerated although it does not multiply. The bacterium is destroyed by pasteurisation of milk and cooking of food, but the toxin may survive these processes. The main foods associated with illness are cooked meats, poultry and foods which are handled during preparation without subsequent cooking.

Symptoms: Onset of symptoms varies between 2 and 6 hours. Symptoms are severe vomiting, abdominal pains and diarrhoea. They generally last no longer than 2 days.

NORWALK-LIKE VIRUSES

 (Previously know as Small Round Structured Viruses or SRSVs) Norwalk-like viruses are the commonest food borne viral infection and are usually spread from person to person.

Characteristics: Norwalk-like viruses are transmitted from person to person (e.g. by projectile vomiting), environmental contamination and contaminated water. Food borne infection may be associated with sewage contamination of shellfish or fresh produce, or contamination by an infected food handler. Outbreaks occur most frequently in nursing homes and hospitals due to person to person spread.

Symptoms: Norwalk-like viruses cause an acute gastro-enteritis and are the commonest cause of viral gastro-enteritis epidemics. Symptoms include vomiting and diarrhoea. The symptoms take 12-48 hours to develop, and last for about 2 days