Trading Standards Institute Advice

Food borne illness and contamination: Salmonella

This leaflet is for all food businesses, including those involved in food preparation and production, catering businesses, retail premises, restaurants, pubs, cafes, and takeaway and fast-food shops.

What is Salmonella?
Salmonellosis is the illness that develops after eating foods contaminated with Salmonella bacteria.

According to the World Health Organisation, it is one of the most common food borne diseases. Each year, millions of cases are reported worldwide and the disease results in thousands of deaths.

There are now over 2,500 known types of Salmonella.

What causes Salmonella?
The bacteria live in the intestines of infected animals and humans.

Most outbreaks of Salmonella food poisoning are caused by Salmonella typhimurium and Salmonella enteritidis. Salmonella typhi can cause typhoid fever, a very serious illness.

Pets and humans can carry the bacteria and, although they may show no symptoms, they can pass the illness on to others. 

Salmonella bacteria are often found in food such as:

  • raw meat
  • poultry
  • unpasteurised milk
  • dairy products
  • seafood

The bacteria does not usually affect the taste, smell, or appearance of food.

Prepared foods, such as sandwiches, that have been touched by infected food handlers can be a danger, as can food that has been washed in contaminated water.

Touching pets or pet faeces (droppings) and then not washing your hands properly before cooking or eating can be enough to introduce an infection that leads to illness.

What are the effects or symptoms caused by Salmonella poisoning?
The bacteria attack all age groups. Children, elderly people and people who are already ill are much more likely to get a serious infection. 

Usually the symptoms develop within 12 to 36 hours of eating food contaminated with the bacteria.

Symptoms can include headache, nausea (feeling sick) and vomiting (being sick), stomach cramps and severe diarrhoea, chills and sweating. Dehydration is a danger because the person may lose more water than they can take in if they are being sick straightaway when trying to drink. 

In mild cases, there are fewer symptoms, possibly only diarrhoea, which may last for four to seven days. In severe cases, symptoms can last longer and some doctors consider it appropriate to treat with antibiotics.

If someone is infected with Salmonella they should see a doctor as salmonellosis is a 'notifiable disease' under the Public Health (Infectious Diseases) Regulations 1988 and the Public Health (Control of Diseases) Act 1984.

With some sufferers it may be several months before their bowel habits return to normal. A small number of people may develop pains in their joints, irritation of the eyes, and it may be painful when they urinate. In serious cases this can last for many months and can lead to chronic arthritis.

How does food get contaminated?
Most cases of illness are caused when bacteria pass from raw food to ready-to-eat food. If ready-to-eat food is not stored properly, for example, it is not put in the fridge, the bacteria multiply to a point when people eating the food will become ill. When preparing large quantities of food, whole batches can become contaminated by Salmonella and many people may be affected before the source of the infection is identified and stopped.

The cells of Salmonella bacteria cannot multiply below 4°C, so you should keep high-risk food in a fridge set between 1°C and 4°C. 'High risk' is the term used for food that is most likely to cause food poisoning, such as any food that is ready to eat (including cooked rice, cooked meats, shellfish and dairy products such as milk and cream).

How can I control or prevent Salmonella?
Use a thermometer to regularly check that your fridge is keeping food at the correct temperature.

Thoroughly defrost food such as frozen chicken in the bottom of a fridge before you cook it. You should then thoroughly cook the meat all the way through to a minimum temperature of 75°C in the middle of the thickest part of the meat.

Using a temperature probe (food thermometer) to check the temperature in the middle of the thickest part of food is the easiest way of making sure food is cooked thoroughly.

Cooking food thoroughly will kill Salmonella, but it may still be spread from contaminated raw food to cooked and ready-to-eat food if a kitchen does not follow good hygiene practices.

If your staff are ill, make sure they report this immediately. A 'healthy carrier' is someone who carries the Salmonella bacteria and is able to pass it on to others, but shows no symptoms themselves.

Staff must report symptoms of illness to their supervisor or business owner and should not be allowed to work around food until at least 48 hours after all symptoms have disappeared or, ideally, until a doctor has said they are well enough to return to work.

Although the chances of eggs being contaminated are now low, vulnerable people (such as elderly people, children, pregnant women and people who are already unwell) are more at risk. Cooking eggs thoroughly will kill the bacteria - so make sure that the eggs they eat are cooked thoroughly to reduce the risk of food poisoning.

In the UK, eggs and poultry are checked regularly to make sure they do not contain large amounts of Salmonella, but you should still take care. Eggs cannot be guaranteed to be Salmonella-free, wherever they come from. 

The British Egg Information Service brought back the Lion Quality Mark in 1998. To be allowed to print this mark on their eggs, farms are checked for food-hygiene standards and all chickens that lay eggs must be vaccinated against certain types of Salmonella. The eggs must be marked with a 'best before' date to help with stock rotation, and also a mark identifying the farm they came from, so they can be traced back.

Make sure all staff follow good personal-hygiene routines, including hand-washing routines. Staff must be trained to help avoid food contamination.

Make sure all staff wash their hands when switching from preparing one type of food to another, especially before preparing cooked or ready-to-eat food.

Wash kitchen utensils thoroughly before you use them with another type of food.

Use different cutting boards and knives for preparing different foods.

Use disposable paper cleaning cloths to clean contaminated areas and equipment. Make sure different cloths are used for different jobs. Change re-usable cloths at least every day and wash them in hot water and detergent in order to clean and disinfect them.

Keep the food areas and premises pest-free.

Do not allow pets in the food-preparation or storage areas.

Store high-risk foods in the fridge (between 1°C and 4°C). Do not leave meat, poultry and fish out of the fridge for long periods of time.

Store raw meat and vegetables separately from cooked food and salads - use separate fridges if possible, but if this is not practical keep raw food covered and stored below ready-to-eat foods.

The design of your premises should allow for an efficient workplace, keeping raw food processes away from cooked food processes.

Make sure frozen poultry is thoroughly thawed and then thoroughly cooked.

Make sure poultry and eggs are thoroughly cooked.

Make sure that your food-safety management system identifies the hazards associated with Salmonella, states how to make sure food is stored, prepared and cooked correctly and how these factors are to be checked and monitored.

More information
You will find further guidance in our other leaflets on this website. Information can also be found on the Food Standards Agency website.

Alternatively, contact your local environmental health service for advice.

Please note
This leaflet is not an authoritative interpretation of the law and is intended only for guidance.

© 2018 itsa Ltd.