A food-borne illness or food poisoning is any illness resulting from the consumption of food contaminated with pathogenic bacteria, toxins, viruses, prions or parasites. Such contamination usually arises from improper handling, preparation or storage of food. Good hygiene practices before, during, and after food preparation can reduce the chances of contracting an illness. The action of monitoring food to ensure that it will not cause food-borne illness is known as food safety.
Some common diseases are occasionally transmitted to food through the water vector. These include infections caused by Shigella, Hepatitis A, and the parasites Giardia lamblia and Cryptosporidium parvum. Contact between food and pests, especially flies, rodents and cockroaches, are other food contamination vectors.
Food-borne illness can also be caused by the presence of pesticides or medicines in food, or by unintentionally consuming naturally toxic substances like poisonous mushrooms or reef fish.
Symptoms and mortality
Symptoms typically begin several hours after ingestion and depending on the agent involved, can include one or more of the following: nausea, abdominal pain, vomiting, diarrhea, fever, headache or tiredness. In most cases the body is able to permanently recover after a short period of acute discomfort and illness. However, foodborne illness can result in permanent health problems or even death, especially in babies, pregnant women (and their fetuses), elderly people, sick people and others with weak immune systems. Similarly, people with liver disease are especially susceptible to infections from Vibrio vulnificus, which can be found in oysters.
The infectious dose is the amount of agent that must be consumed to give rise to symptoms of food-borne illness. The infective dose varies according to the agent and consumer's age and overall health. In the case of Salmonella, as few as 15-20 cells may suffice
The delay between consumption of a contaminated food and appearance of the first symptoms of illness is called the incubation period. This ranges from hours to days (and rarely months or even years), depending on the agent, and on how much was consumed. If symptoms occur within 1-6 hours after eating the food, it suggests that it is caused by a bacterial toxin rather than live bacteria.
During the incubation period, microbes pass through the stomach into the intestine, attach to the cells lining the intestinal walls, and begin to multiply there. Some types of microbes stay in the intestine, some produce a toxin that is absorbed into the bloodstream, and some can directly invade the deeper body tissues. The symptoms produced depend on the type of microbe.
Preventing bacterial food poisoning
The prevention is mainly the role of the state, through the definition of strict rules of hygiene and a public service of veterinary survey of the food chain, from farming to the transformation industry and the delivery (shops and restaurants). This regulation includes:
· Traceability: in a final product, it must be possible to know the origin of the ingredients (originating farm, identification of the harvesting or of the animal) and where and when it was processed; the origin of the illness can thus be tracked and solved (and possibly penalized), and the final products can be removed from the sale if a problem is detected;
· Respect of hygiene procedures like haccp and the "cold chain";
· Power of control and of law enforcement of the veterinarians.
· At home, the prevention mainly consists of:
· Separating foods while preparing and storing to prevent cross contamination. (i.e. Clean cutting boards, utensils, and hands after handling meat and before cutting vegetables, etc.)
· Washing hands and/or gloves before handling ready-to-eat foods.
· Respecting food storage methods (hot foods hot and cold foods cold) and food preservation methods (especially refrigeration), and checking the expiration date;
· Avoiding over-long storage of left-overs;
· Washing the hands before preparing the meal and before eating;
· Washing the fresh fruits and vegetables with clear water, especially when not cooked (e.g. Fruits, salads), scrubbing firm fruits and vegetables with a brush to clean;
· Washing the dishes after use, rinsing them well in hot water and storing them clean and dry;
· Keeping work surfaces and chopping boards clean and dry;
· Keeping the kitchen and cooking utensils clean and dry;
· Not relying on disinfectants or disinfectant-impregnated cloths and surfaces as a substitute for good hygiene methodology (as above);
· Preventing pets walking on food-preparation surfaces.
· Bacteria need warmth, moisture, food and time to grow. The presence, or absence, of oxygen, salt, sugar and acidity are also important factors for growth. In the right conditions, one bacterium can multiply using binary fission to become four million in eight hours. Since bacteria can be neither smelled nor seen, the best way to ensure that food is safe is to follow principles of good food hygiene. This includes not allowing raw or partially cooked food to touch dishes, utensils, hands or work surfaces previously used to handle even properly cooked or ready to eat food.
High salt, high sugar or high acid levels keep bacteria from growing, which is why salted meats, jam, and pickled vegetables are traditional preserved foods.
The most frequent causes of bacterial food-borne illnesses are cross-contamination and inadequate temperature control. Therefore control of these two matters is especially important.
Thoroughly cooking food until it is piping hot, i.e. above 70 °C (158 °F) will quickly kill virtually all bacteria, parasites or viruses, except for Clostridium botulinum and Clostridium perfringens, which produces a heat-resistant spore that survives temperatures up to 100 °C (212 °F). Once cooked, hot foods should be kept at temperatures out of the danger zone. Temperatures above 63 °C (145 °F) stop microbial growth.
Cold foods should also be kept colder than the danger zone, below 5 °C (41 °F). However, Listeria monocytogenes and Yersinia enterocolitica can both grow at refrigerator temperatures.
Hot foods should be held at 57°C (135 °F) or hotter until ready to cool. Hot foods need to be cooled quickly to limit the amount of time the food is in the danger zone (temperature range at which bacteria can grow.) The food should be cooled from 57 °C (135 °F) to 20 °C (70 °F) within two hours. Then further chilled to less than 5 °C (41 °F) in 4 hours. Food should then be held chilled at 5 °C (41 °F) or less.
Viral infections make up perhaps one third of cases of food poisoning in developed countries. They are usually of intermediate (1-3 days) incubation period, cause illnesses which are self-limited in otherwise healthy individuals, and are similar to the bacterial forms described above.
· Norovirus (formerly Norwalk virus)
· Hepatitis A is distinguished from other viral causes by its prolonged (2-6 week) incubation period and its ability to spread beyond the stomach and intestines, into the liver. It often induces jaundice, or yellowing of the skin, and rarely leads to chronic liver dysfunction.