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Food Poisoning Symptoms: What You Should Know

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Food poisoning symptoms are caused by a large number of bacteria. But the most common as listed below:

  1. E.coli (O157)
  2. Staphylococcus aureus
  3. Salmonella enteritidis
  4. Listeria monocytogenes
  5. Clostridium species
  6. Campylobacter species

Each of these types of bacteria causes what is commonly known as food poisoning symptoms and are similar in the ways that the cause food-borne illness.

Food poisoning symptoms can be defined as an illness caused by consuming food or drink that has been contaminated, causing nausea, vomiting or diarrhoea. CDC

Food poisoning symptoms can be mild with a running tummy to severe dehydration causing hospitalisations. Exposure to toxins from bacteria in severe cases can cause death.

Testing for Food Poisoning

The recent Listeriosis outbreak in South Africa, which is the largest outbreak in the world to date, is a perfect example of this.

There are three sources in the food that can cause contamination:

  • Physical (Rust, paint, glass, wood.)
  • Chemical (Non-food safe chemicals, such as Bleach, High concentrations of Chlorine, ammonia.)
  • Biological (Bacteria, Moulds, viruses and pests.)

These sources of contamination can be introduced into the kitchen, by unsafe practices in the kitchen itself, or during the production/manufacturing process.

If your illness is severe or complicated, your doctor may run some of the following tests.

  • Stool tests are the most common lab test done for food poisoning. 
  • A medical doctor may order one if you have a fever or abdominal pain. 
  • A sample of your stool can help tell if your illness is related to bacteria. 
  • Blood samples are also tested and can be used to identify the exact bacteria causing the illness. 
  • These can be genotyped using whole genome sequencing
  • The recent Listeriosis outbreak in South Africa shows how effective these tests can be.   

How common are food related illnesses and food poisoning symptoms?

The World Health Organisation (WHO) says that 1 in 10 people worldwide, fall sick from food poisoning. Within that 10%, 420 000 people worldwide incur severe infections or complications from food poisoning and die from food poisoning each year.

In 2007 The Food Standards Agency (FSA) estimates that there are around 850,000 cases of food poisoning each year in the UK. The FSA estimates that there are 500 deaths from food poisoning in the UK every year.

Foodborne illness, better known as the dreaded food poisoning, causes almost 50 million illnesses and 3,000 deaths annually in the United States.

According to the Centre for Disease Control of America (CDC), foodborne illness, better known as food poisoning is a common, costly, yet preventable public health problem. The impact of food poisoning is not only health related, but also affects the economy, through the loss of productive time (sick leave), the impact on the health care system, as well as loss of revenue of food business who have either caused food poisoning unintentionally or through negligence.

Food Poisoning Symptoms

Food borne illness, better known as the dreaded food poisoning, causes almost 50 million illnesses and 3,000 deaths annually in the United States.

There are many different food-borne infections and more than 250 different food-borne diseases that have been described. Most of these diseases are infections caused by a variety of bacteria or because of the toxins that they produce.

These diseases have a variety of symptoms and there is not one condition that is known to be a defining factor of food-borne illness, especially when we consider that many hospitalisation cases, actually occur as a result of dehydration, rather than physical ‘poisoning’.

The symptoms of food poisoning depend on the type of contaminant and the amount eaten. Food poisoning can develop rapidly within 6 hours or slightly worsening over a few days. Most of the common contaminants caused nausea, vomiting, diarrhoea and abdominal cramping. Usually, food poisoning is not serious and the illness runs its course within 24 to 48 hours. However, food poisoning can happen within 6 hours in serious cases otherwise up to 24 hours.

Raw foods of animal origins are the most likely causes of contamination, such as raw meat and poultry, raw eggs, unpasteurised milk and raw shellfish.

If we consider today’s manufacturing processes, a single hamburger may contain meat from hundreds of different animals. A glass of raw milk may contain milk from hundreds of different cows. Thus, the potential for food poisoning is quite high when you look at these figures.

Raw fruits and vegetables are of a particular concern however washing can decrease but not eliminate the contamination. A number of outbreaks have been traced to the fresh fruits and vegetables that were produced under less than sanitary conditions, especially in European countries such as Germany and Spain.

Water Quality is Important

These outbreaks show that the quality of the water used for washing and chilling produce after harvest is critical. Using water that is not clean can contaminate many boxes of produce. Fresh manure used to fertilise vegetables can also be a contaminant. This is an important factor to consider now, that organic farming has become so popular. 

As we already mentioned E.coli occurs naturally in the gut of mammals. Raw milk and unpasteurised fruit juice has also been shown to be a contaminant of pathogens. This also includes the fruits these juices are made from.

Many foodborne microbes are present in healthy animals as they exist within their intestines. However, meat and poultry caucuses can become contaminated during the slaughter process by contact with small amounts of intestinal contents.

Certain types of Salmonella can affect a hens’ ovary so that the internal contents of a normal egg can be contaminated with Salmonella without even breaking the shell.

Oysters and other filter feeding shellfish can concentrate a bacterium called Vibrio that is naturally present in seawater.

Similarly, fruit juice and vegetables can be contaminated if they are washed or irrigated with water that is contaminated with animal manure or human sewage. 

  • Food poisoning symptoms depend on the type of contaminant and the amount eaten.
  • Can develop rapidly, within 2 hours, or slowly, worsening over days to weeks.
  • Most of the common contaminants cause nausea, vomiting, diarrhoea, and abdominal cramping.
  • Poisoning can happen within 2 – 6 hrs in serious cases, otherwise up to 24hrs.
  • Mild forms of food poisoning result in Diarrhea (runny tummy).

Many food-related illnesses and food poisoning symptoms carry many of the same symptoms and are often asymptomatic (no specific symptom that tells us its Salmonella, E.coli, Staph aureus).

There is an exception with Listeriosis, that causes infection of the nervous system, presenting neck pain, confusion and flu-like symptoms in addition to the regular cramping and runny tummy.

How to Treat Food Poisoning Symptoms

Nausea and Vomiting

  1. Avoid solid foods until vomiting ends.
  2. Eat light, bland foods. Toast is usually the best.
  3. Sip liquids to prevent vomiting.
  4. Don’t eat fried, greasy, spicy, or sweet foods.


  1. Drink clear liquids, starting with small sips and gradually drinking more.
  2. If vomiting and diarrhoea last more than a day, drink a rehydrate solution.

When to Call a Doctor

Call a doctor immediately if symptoms last more than 3 days or you have:

  1. Severe belly pain
  2. Fever
  3. Bloody diarrhoea or dark stools
  4. Vomiting that is prolonged or bloody
  5. Signs of dehydration, such as dry mouth, decreased urination, dizziness, fatigue, or increased heart rate or breathing rates.

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