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Food poisoning and infectious diseases - what to do

Environmental health will investigate certain types of food poisoning and infectious diseases to see if there is information which can help identify a cause, or if there is evidence of a wider problem within the local community.

Most cases will be a one off, and are identified as a result of the person suffering illness going to their GP and being tested to identify the cause of illness. Environmental health will work with colleagues in NHS Lothian to ensure that the illness does not spread any further through person to person contact, or through further contamination of food, drink or other source (e.g. water sport, drinking water, camping, animal contact etc.)

If you think you have become ill as a result of eating food or drink, or through other activities then you should contact your GP to seek medical advice, and request that samples are taken to identify the cause of infection. If any tests confirm the following types of infection causing organisms were involved, then it is likely that follow up investigations will be carried out by ourselves, or NHS Lothian (some further information is provided on each of these).

  • Salmonella.
  • E coli O157
  • Campylobacter.
  • Giardia.
  • Cryptosporidium.
  • Legionella.
  • Listeria

What should I do if I am ill?

As already mentioned above the first thing to do is seek medical advice from your GP.

Most infections which cause symptoms such as diarrhoea and vomiting are a concern because they can be spread to other people through poor hygiene. In such cases it is always important to ensure you are not preparing or handling food for other people, and that you are not sharing hand towels etc. while you are still unwell. Wash all dirty clothes, bedding and towels in the washing machine on the hottest cycle possible. Clean toilet seats, toilet bowls, flush handles, taps and wash hand basins after use with detergent and hot water, followed by a household disinfectant.

If you work with food, in health care or with vulnerable people you may have to be formally excluded from work. If you work with food etc. you should advise your employer and avoid normal duties until you have been symptom free for at least 48 hours, or until any formal exclusion from work has been removed.

Further information on Food poisoning and infectious diseases:


Symptoms include diarrhoea, stomach cramps and sometimes vomiting and fever.

On average, it takes from 12 to 72 hours for the symptoms to develop after swallowing an infectious dose of salmonella.

Symptoms usually last for four to seven days and most people recover without treatment.

You usually get salmonella by eating contaminated food. Salmonella bacteria live in the gut of many farm animals and can affect meat, eggs, poultry and milk. Other foods like green vegetables, fruit and shellfish can become contaminated through contact with manure in the soil or sewage in the water.

Contamination is also possible if raw and cooked foods are stored together. Most tortoises and terrapins and other pet reptiles can also carry salmonella. Dogs, cats and rodents can occasionally become infected.

It is impossible to tell from its appearance whether food is contaminated with salmonella. It will look, smell and taste normal.

Salmonella can be spread from person to person by poor hygiene, by failing to wash your hands properly after going to the toilet, or after handling contaminated food.

E coli O157

Symptoms include diarrhoea, stomach cramps and occasionally fever. About half of people with the infection will have bloody diarrhoea.

People usually notice symptoms three to four days after they have been infected, but symptoms can start any time between one and 14 days afterwards.

These symptoms can last up to two weeks.

A small number of people with E. coli O157 infection go on to develop a serious condition called haemolytic uraemic syndrome (HUS). This can sometimes lead to kidney failure and death, although this is rare. The risk of HUS is highest in children aged under five years

E. coli O157 is found in the gut and faeces of many animals, particularly cattle. It is an uncommon cause of gastroenteritis but can be caught by:

  • eating contaminated food (such as raw leafy vegetables or undercooked meat)
  • touching infected animals or accidentally coming into contact with their faeces
  • contact with people who have the illness, particularly if you do not wash your hands thoroughly after using the toilet or before handling food
  • drinking water from inadequately treated water supplies
  • swimming or playing in contaminated water, such as ponds or streams

Symptoms include diarrhoea, vomiting, stomach pains and cramps, fever, and generally feeling unwell. They usually develop within 2 - 5 days, but can take as long as 10 days. Most cases start to clear up after 2 - 3 days of diarrhoea and, 80% to 90% settle within 1 week.

Campylobacter is found in most raw poultry and is common in raw meat. Mushrooms and shellfish can also be contaminated but this is unusual. Avoid storing raw and cooked foods together and don't use the same work surfaces, or utensils when preparing raw and cooked food. You can also get Campylobacter from infected pets and other animals.


Diarrhoea is the most common symptom of giardiasis. Other symptom may be present, including stomach cramps, bloating, nausea etc. They can develop within 5 - 25 days.

Most people become infected with giardiasis by drinking water contaminated with the Giardia parasite, or through direct contact with an infected person.

The giardiasis infection can also be passed on if an infected person doesn't wash their hands properly after using the toilet, then handles food eaten by others. Food can also be contaminated if it is washed with infected water.


The most common symptoms are watery diarrhoea, vomiting, stomach pains, and fever which may only last a couple of days, but which can continue for up to three or four weeks. It can affect people with weak immune systems for much longer. You might think that you are getting better and have shaken off the infection but then find that you get worse before the illness eventually goes. Symptoms usually appear within 1 week, but can appear anytime between 1 - 12 days.

Cryptosporidium is found in lakes, streams and rivers, untreated drinking water and sometimes in swimming pools. You can get cryptosporidiosis directly from another person or animal by touching faeces, (for example when changing a nappy) and putting your hands near or in your mouth without washing them thoroughly. You can also get cryptosporidiosis from infected animals or by swimming in, or drinking contaminated water. Occasionally you can be infected by eating and drinking contaminated food, particularly unpasteurised milk, under cook meat and offal (liver, kidneys, and heart).


Legionnaires disease is the most common infection caused by legionella bacteria. Unlike other infections mentioned above it cannot be spread person to person.

Initial symptoms usually include flu-like symptoms, such as:

  • mild headaches
  • muscle pain
  • high temperature (fever), usually 38C (100.4F) or above
  • chills
  • tiredness
  • changes to your mental state, such as confusion

Once bacteria begin to infect your lungs, you may also experience symptoms of pneumonia, such as:

  • a persistent cough - which is usually dry at first, but as the infection develops you may start coughing up phlegm or, rarely, blood
  • shortness of breath
  • chest pains

Symptoms normally appear within 6-7 days, but it can be as long as 19 days.

Legionella bacteria is usually found (often in harmlessly low numbers) in sources of water, such as ponds, rivers and lakes. However, the bacteria can rapidly multiply if they find their way into artificial water supply systems, such as air conditioning systems.

Large buildings, such as hotels, hospitals, museums and office blocks, are more vulnerable to Legionella contamination because they have larger, more complex water supply systems in which the bacteria can quickly spread.


In most people, listeriosis is mild and causes symptoms including a high temperature (fever), vomiting and diarrhoea. These symptoms usually pass within three days without the need for treatment. Symptoms can appear between 3 - 70 days.

However, in rare cases, the infection can be more severe and spread to other parts of your body, causing serious complications, such as meningitis. Common signs of severe listeriosis include a stiff neck, severe headache and tremors.

Pregnant women are at particular risk of developing listeriosis. This is because the body's natural defences against the listeria bacteria are weaker during pregnancy.

Listeria bacteria have been found in a range of chilled "ready-to-eat" foods, including:

  • pre-packed sandwiches
  • pâté
  • butter
  • soft cheeses - such as Brie or Camembert, or others with a similar rind
  • soft blue cheese
  • cooked sliced meats
  • smoked salmon

The bacteria may also be passed on through contact with the faeces of infected animals or human carriers.