You will remember that we said that food poisoning is an illness caused by eating food contaminated with harmful substances or micro-organisms living on the food. Well, there is another group of illnesses that can be caught from eating contaminated food. These are the food-borne diseases which, like most food poisoning, are caused by micro-organisms but the microbes that cause food-borne diseases do not live and multiply on food they are just carried by the food.
Food-borne disease is "an illness caused by micro-organisms carried by food or water". Unlike food poisoning bacteria, the bacteria that cause food-borne disease do not multiply whilst on the food, they just survive on the food.
Food-borne diseases include typhoid, dysentery and a particular form of hepatitis. You may well have heard of these but fortunately they are relatively rare in this country. A much more common food-borne disease is something called Campylobacter enteritis (pronounced Camp eye low bacter), which causes severe diarrhoea. In fact, it is the main cause of food-borne disease, being responsible for about 50,000 cases a year.
Only a very small number of micro-organisms are necessary to cause food-borne disease and they can be carried by water as well as food. Whilst, as in food poisoning, the incubation period for food-borne diseases can be a few days, with some diseases it may be several weeks or even months. Some of the symptoms of food-borne diseases are similar to those of food poisoning e.g. diarrhoea and high temperature. But other food-borne diseases can produce very different symptoms including paralysis, kidney failure and meningitis (inflammation of the lining of the brain).
One other food-borne disease that you may well have heard of is the illness caused by Escherichia coli O157, better known by its shorthand name of E. coli O157. Again, only very few E. coli bacteria are required to make people ill and, particularly in the case of children and the elderly, it can be a very serious condition. E. coli O157 was responsible for Britain's most deadly outbreak of food-borne disease. In 1996 eighteen people died after eating E. coli contaminated food bought from a Lanarkshire butcher. More details of E. coli are given later.
Most of the cases of food poisoning that occur are caused by the contamination of food with harmful bacteria. Bacteria are micro-organisms, which are living creatures so small they can only be seen through a powerful microscope. Although bacteria are the greatest threat to food, viruses and moulds are other micro-organisms that can contaminate food and cause illness. Besides bacteria and other micro-organisms, food poisoning can also be caused by chemicals and metals that contaminate food and by the consumption of poisonous plants and fish. In most cases of food poisoning, whatever the cause, the illness is one that affects the gastrointestinal system (the gut). The usual symptoms include diarrhoea and/or nausea and vomiting. It is also quite common for patients to have a high temperature and headache.
Although this course will be mainly concerned with food poisoning, you need to know that there are other diseases that can be carried by contaminated food and which, unlike food poisoning, are so infectious that only a few organisms are needed to make people ill. These are food-borne diseases and include typhoid, dysentery, Campylobacter enteritis and illness due to E. coli.