A number of factors contribute to the risks of illness following consumption of contaminated foods.
Have you ever wondered why some people get ill after consuming contaminated food or drink, but others do not, even though they may have eaten the same thing? A number of factors contribute to the risks of illness following consumption of contaminated foods.
The terminology that most of us grew up with when referring to foodborne illness or foodborne disease was food poisoning. The term food poisoning, although still widely used, is misleading, because most foodborne diseases are infections rather than poisoning caused by toxins or chemicals. Foodborne disease, by World Health Organization definition, is any infectious or toxic disease associated with consumption of food or water, and includes illness caused by bacteria (e.g. Salmonella, E. coli 0157 and Campylobacter), viruses (e.g. Norwalk-like virus), parasites (e.g. Cyclospora and Cryptococcus), fungi (e.g. poisonous mushrooms), and chemicals (e.g. arsenic). Common symptoms of foodborne disease are nausea, vomiting, abdominal cramps and diarrhea.
Foodborne disease may be due to infection or intoxication. Foodborne infection occurs when bacteria, viruses or parasites are consumed in food. Intoxication or poisoning occurs when food has been contaminated with harmful toxins or chemicals - intoxication may result from chemicals such as arsenic, plant, fungal or shellfish toxins, as well as bacterial toxins already present in food in large enough amounts to result in illness. Intoxication tends to have a more rapid onset than infection, and intense vomiting is often the prominent symptom, as the body attempts to rid itself of the harmful toxin or chemical.
Infection involves an incubation period of variable duration ranging from hours to days depending on the individual properties and virulence factors of the contaminating organism, and the number swallowed. A sufficient number of organisms must be consumed to cause illness - this is referred to as the infectious dose. The infectious dose varies from one organism to another. Relatively small numbers of Campylobacter (as few as 500) bacteria can cause infection; whereas, larger numbers of Salmonella ( 100,000) are required to cause infection. Bacteria have to be present in large enough numbers that some survive stomach acids and pass to the intestines where they attach to the intestinal cell wall and multiply. Attachment prevents the bacteria from being flushed out of the body. As the organisms multiply in number, they reduce the capacity of the gut to absorb water, resulting in excess fluid volume in the large intestine and diarrhea. As the organisms multiply in number, they may produce toxins that damage the intestinal lining or other organ systems (e.g. kidney damage resulting from hemolytic uremic syndrome caused by E. coli 0157. Some organisms stay in the intestine, but other types can actually penetrate or invade the intestinal lining producing inflammation, abscesses, ulcers, and possible spread to the bloodstream and/or other areas of the body.
In addition to having sufficient numbers of organisms to cause illness, host factors also determine whether an individual gets ill, and the attack rate or number of cases involved in an outbreak of foodborne illness. The very young, very old, and immunocompromised individuals are much more likely to become ill, and to have more severe illness than healthy adults. Whereas, small numbers of contaminating organisms may cause illness in an immunocompromised person, large numbers would be required to cause illness in most healthy adults. Additionally, healthy adults may show some protection against subsequent infection if previously exposed to the same agent - this type of protection is known as acquired immunity.
Foodborne Illness Prevention Courses:
Hazard Analysis Critical Control Point (HACCP) Course
