Food poisoning is an illness caused by the consumption of contaminated food or water. Food poisoning must meet two criteria, namely: it must affect a minimum of two persons, and there must be evidence of food as the cause.
Food poisoning is caused by infectious agents such as viruses, bacteria and parasites, or toxic agents such as poisonous mushrooms, or pesticides on fruits and vegetables.
Contamination usually occurs from the following: leaving prepared food at temperatures that allow bacterial growth, inadequate cooking or reheating, cross-contamination with contaminated food, and infection from food handlers who are already infected.
The symptoms depend on the type of contaminant and the amount eaten. These develop rapidly within 30 minutes, or slowly within a day or two of consuming a contaminated food or drink.
Typical symptoms include nausea, vomiting, abdominal cramping, headache and diarrhea . Occasionally, fever, chills, bloody stool and dehydration may occur.
These symptoms will more often than not affect more than one person who ate the same thing. In rare cases, the nerves, liver and kidney may be affected, leading to permanent disability or death.
Food poisoning is mainly diagnosed based on clinical symptoms.
Diarrhoea lasting more than two weeks is almost always not as a result of food poisoning and must be investigated thoroughly. Fever, though uncommon, may be present, but this too needs to be investigated for other causes such as amoebiasis.
Should the diagnosis be unclear, a stool test may be carried out to check for cysts of parasites. Bacterial culture for organisms is mandatory in cases of unrelenting fever or symptoms persisting for longer than three to four days.
Most cases of food poisoning are self limited, and treatment is mainly symptomatic, with an objective of adequate rehydration and electrolyte supplementation. This can be achieved with either oral rehydration solutions (ORS) or intravenous fluids.
A simple ORS may be made with one level teaspoon of salt and four heaped teaspoons of sugar added to one litre of water. The use of ORS has reduced the mortality rate associated with cholera from higher than 50 per cent to less than 1 per cent.
Intravenous solutions are recommended for patients who are severely dehydrated or who have intractable vomiting.
In the absence of dysentery (bloody diarrhoea), antibiotics are unnecessary, unless laboratory confirmation of a bacterial agent is confirmed. Most people begin feeling better within a day or two.
Nausea and slight diarrhoea may however last a day or two days longer.
It is important that safe steps in food handling, cooking and storage are taken to prevent food poisoning. These precautions include:
• Buy foods before the “sell by” date.
• Raw meat should be stored separately from other foods.
• Cold foods should be bought last and taken home fast.
• If possible, refrigerate all perishable foods
• Place raw meat in the coldest section of your refrigerator.
• When preparing food, keep everything clean.
• After cutting raw meats, wash hands, cutting board, knife, and counter tops with hot, soapy water.
• Fridge-thawing is the safest way to thaw food. Ensure that thawing juices do not drip on other foods.
• Cook meat immediately after microwave thawing.
• While cooking meat, ensure it is well done to rid it of all live parasites.
• Keep cold food cold and hot foods hot.
• Do not leave food sitting out for more than two hours, as bacteria that cause food poisoning grow rapidly at room temperature.
• Use cooked leftovers within four days.
The writer is a medical doctor and a public health specialist. Do you have any health-related questions? Write to [email protected]