Food poisoning explained: Is food poisoning really what you think it is?

Emeh Joy

Contrary to what some people think food poisoning means, food poisoning is when you eat contaminated food. Depending on the severity and type of contaminant, it can lead to the death of an affected individual. 

A sick girl suffering from food poisoning

What comes to your mind when you hear "food poisoning".

You might be familiar with stories of people adding 'poison' to another person's food to terminate the other person's life. Such a scenario is what comes to the mind of many when they hear "food poisoning".

While manipulation of food by a third party via adulteration, contamination or addition of high doses of a chemical can cause food poisoning, it is not all that is to food poisoning.

Food poisoning is also called foodborne illness or foodborne disease. It occurs when a person eats contaminated, toxic or spoilt food, whether deliberately or accidentally. Many bacteria, viruses and parasites in the ecosystem are culprits here.

Accidental food poisoning is quite common and occurs when a victim unknowingly ingests food contaminated by certain microorganisms or toxic substances. 

The microorganisms that cause foodborne diseases are often associated with the digestive tracts of humans, birds and other animals.

According to the Centers for Disease Control and Prevention (CDC), one in six Americans will contract some form of the illness each year.1

Also, the World Health Organisation reported that about 600 million people fall ill after eating contaminated food, and about 420,000 die every year. It added that eating contaminated food causes more than 200 diseases.3

Causes of food poisoning

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Different toxic agents, when present in food, can cause food poisoning. However, major causes of food poisoning include:


Bacteria is the most common cause of food poisoning. Among the most dangerous bacteria are Listeria, E.coli and Salmonella

Salmonella is the most common culprit. They can grow and multiply in meat products kept at room temperature; products like sausages, meat pies, sandwiches, ham and bacon. CDC reported that salmonella infection can be linked to about 1,000,000 cases of food poisoning every year.2

Other bacteria that are culprits include Bacillus cereus, Vibrio Cholerae Staphylococcus aureus, Clostridium botulinum, Shigella species, and others that produce toxins that can cause foodborne illnesses intoxications.

Listeria monocytogenes survive temperatures below 5°C. This means they can multiply in refrigerated food; however, they can be eradicated by thorough cooking and pasteurization.


Viruses also cause food poisoning. According to the CDC, norovirus causes more than 19 million cases of food poisoning every year. 

Hepatitis A is a severe condition that causes liver infection. The hepatitis A virus is typically transmitted through food.

Rotavirus, sapovirus and astrovirus can also cause severe food poisoning symptoms, but they are less common. 


Food poisoning due to parasitic infection is not as common as those caused by bacterial infection. However, parasites that spread through food are still dangerous. 

Most times, parasitic contamination of food is caused by Toxoplasmais. This parasite is commonly found in cat litter boxes.

Parasites can live for years in the digestive tract undetected. However, pregnant women and people with a weak immune system are more likely to develop severe side effects. 

Toxic substances

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Aside from microorganisms, other toxic agents like organic pollutants in the soil, allergens, drug residues, agrochemicals and heavy metals like mercury, lead and cadmium can cause food poisoning.

Some toxic chemicals can get washed down into streams and other water bodies contaminating fish. When such contaminated fish is consumed by humans, it can lead to food poisoning.

Also, some substances released into food by bacteria, insects or other living organisms can be harmful to health. The released substances, called toxins, can also cause food poisoning.

Symptoms of food poisoning

Food poisoning is usually symptomatic, and symptoms can vary depending on the source of the infection. 

Symptoms can take as fast as one hour or as long as 28 days to appear, depending on the source of the infection. 

Food poisoning presents with symptoms like:

  • Vomiting
  • Abdominal cramps
  • Diarrhoea
  • Weakness
  • Mild fever
  • Headaches
  • Nausea
  • Loss of appetite

Sometimes food poisoning can be life-threatening. In such cases, an infected person may start experiencing symptoms such as:

  • A high fever of more than 101.5 degrees Fahrenheit
  • Severe diarrhoea that persists for more than three days
  • Bloody urine
  • Sight and speech problem
  • Dry mouth and passing of little urine (symptoms of severe dehydration)

How to prevent food poisoning

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It is not uncommon to find pathogens in our food. Foods like raw meat, milk, poultry, raw vegetables and seafood are more prone to carrying food poisoning microorganisms.

Eating these foods put you at risk of developing foodborne diseases, but we can't stop eating them because they are healthy.

The good thing is that heat from cooking kills most pathogens in foods. But, what happens when you eat foods that are not properly cooked? You expose yourself to the risk of food poisoning. 

Things you can do to prevent food poisoning include: 

  • Cook raw food properly before eating
  • Avoid raw or partly cooked eggs
  • Separate raw food from ready-to-eat foods
  • Wash your hands and cooking surfaces before, during and after cooking 
  • Wash all cooking utensils before and after preparing food
  • Wash your hands after coming in contact with human or pets faeces
  • When you have diarrhoea, it is best to avoid cooking for others
  • Refrigerate food or leftovers within two hours of cooking
  • Ensure your refrigerator is at 40 degrees Fahrenheit or below
  • Do not eat food that has stayed beyond its expiry date
  • Wash raw fruits and vegetables properly before eating


  1. Centres for Disease Control and Prevention (2020, March 18). Foodborne Germs and Illnesses. 
  2. Centres for Disease Control and Prevention. (2021, November 18). Salmonella. 
  3. World Health Organisation (2020, April 30). Food Safety.