The deadly listeriosis outbreak that has infected nearly 1000 people in South Africa since January last year and claimed close to 200 lives earlier this year is hopefully a wake-up call to the dangers of food-borne pathogens.
Globally, one in four people are affected every year, reports the South African Food Advisory Consumer Service, but accurate local statistics are not available as most cases go unreported to health agencies.
Here is the lowdown on what health authorities internationally report to be the most common bacteria, viruses and parasites behind food poisoning.
1. Salmonella
Sources
Raw or undercooked eggs, poultry and meat, unpasturised milk and dairy products, and contact with infected animals, reptiles and birds. Because Salmonella bacteria live in the gut, it can be spread via infected food handlers if they don’t wash their hands after using the loo.
Signs
Within 12 to 72 hours, lasting a few days to a week; nausea, cramps, vomiting, diarrhoea and fever.
Safety steps
Cook foods such as eggs, poultry and minced beef well, wash raw fruit and vegetables before peeling, slicing or eating, and wash hands often, especially before and after handling meat and poultry, says Prof Elna Buys, head of Consumer and Food Sciences at the University of Pretoria.
2. Clostridium perfringens
Sources
Mostly big quantities of food left at room temperature. Known as “the buffet germ,” these bacteria multiply fast, and when there are a lot, produce enough toxins to make you sick.
Signs
Within 6 to 24 hours; cramps and diarrhoea.
Safety steps
Cook food well and keep it above 60˚C or below 4˚C. Divide leftovers into small, shallow containers to cool fast, and reheat to at least 70˚C (steaming hot) before serving, says Buys.
3. Campylobacter
Sources
Raw and undercooked poultry, meat and seafood, unpasturised dairy products, untreated water and contaminated foods.
Signs
Within two to five days, lasting up to 10 days; nausea, vomiting, cramps, diarrhoea (sometimes bloody). The bacteria can spread to the bloodstream and be life-threatening.
Safety steps
Cook foods well and use separate cutting boards for raw and cooked foods, wash raw vegetables and fruit before preparing. Freezing reduces the number of bacteria but won’t destroy them all, so heat food well, Buys advises.
4. Staphylococcus aureus
Sources
Foods handled by people who harbour staph on their skin and in their throats and nostrils. The bacteria don’t usually cause illness unless transmitted to food, where they can multiply and produce enough toxins to cause sickness. Unpasteurised dairy products and cold meats are especially at risk, and foods prepared by hand and requiring no additional cooking, like salads, sandwiches and creamy bakery products.
Signs
Within 30 minutes to 6 hours, lasting two days; nausea, cramps, vomiting, diarrhoea.
Safety steps
Wash hands well before touching food, and don’t work with food if you have a nose, eye or skin infection, or a wound on your hands or wrists, says Buys.
5. E coli
Sources
Raw or undercooked minced beef, unpasteurised dairy, raw dough and contaminated water can harbour a dangerous strain, E coli 0157:H7; also, contact with the faeces of infected people if they don’t wash their hands, or infected animals.
Signs
Within one to 10 days, lasting five to 10 days; severe, often bloody diarrhoea, cramps and vomiting, dark urine and facial pallor.
Safety steps
Cook meat and poultry well, wash hands often, and don’t swallow water when playing in lakes, pools or streams, says Buys.
6. Norovirus
Sources
Contact with someone infected with the virus, particularly in crowded areas, or consuming fresh produce, shellfish, fruit, ice and ready-to-eat foods like salads, sandwiches and biscuits prepared by someone infected.
Signs
Within 12 to 48 hours, lasting one to six days; projectile vomiting, cramps and watery diarrhoea, and sometimes mild fever, headache and muscle aches.
Safety steps
Don’t handle foods or beverages when you’re ill, and always wash hands, vegetables and fruits well, says Buys.
7. Toxoplasma gondii
Sources
Undercooked, contaminated meat, contaminated water, and contact with the faeces of infected cats, which can contain these parasites.
Signs
Flu-like body aches, fatigue, fever, but there are often no signs.
Safety steps
Cook and freeze food well, wash fruits and vegetables thoroughly, and wear gloves to clean the kitty litter box, especially if you’re pregnant or have a weak immune system, Buys cautions.
8. Listeria monocytogenes
Sources
Refrigerated, ready-to-eat foods like polony, viennas and deli meats, unpasturised milk, raw and undercooked meat, poultry and seafood, raw sprouts and fruit.
Signs
Within three to 70 days. From mild to intense nausea, vomiting, aches, fever and diarrhoea. The bacteria can invade the bloodstream and cause meningitis, miscarriage, stillbirth and the death of newborns.
Safety steps
Reheat ready-cooked foods to at least 70˚C (dunk vienna sausage in boiling water), wash fruit and vegetables before preparing, wash hands well, and regularly clean your fridge, kitchen and grocery bag, advises Buys.
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