Food poisoning

A term used for any gastrointestinal illness of sudden onset that is suspected of being caused by eating contaminated food. Most cases of food poisoning are due to contamination of food by bacteria or viruses. The bacteria commonly responsible for food poisoning belong to the groups,, and, certain strains of which are able to multiply rapidly in the intestines to cause widespread inflammation. Food poisoning may also be caused by (see listeriosis). Botulism is an uncommon, life-threatening form of food poisoning caused by a bacterial toxin. The viruses that most commonly cause food poisoning are astravirus, rotavirus, and Norwalk virus (which affects shellfish). This can occur when raw or partly cooked foods have been in contact with water contaminated by human excrement. Non-infective causes include poisonous mushrooms and toadstools (see mushroom poisoning), fresh fruit and vegetables contaminated with high doses of insecticide, and chemical poisoning from foods such as fruit juice stored in containers made partly from zinc. The onset of symptoms depends on the cause of poisoning. Symptoms usually develop within 30 minutes in cases of chemical poisoning, between 1 and 12 hours in cases of bacterial toxins, and between 12 and 48 hours with most bacterial and viral infections. Symptoms usually include nausea and vomiting, diarrhoea, stomach pain, and, in severe cases, shock and collapse. Botulism affects the nervous system, causing visual disturbances, difficulty with speech, paralysis, and vomiting. The diagnosis of bacterial food poisoning can usually be confirmed from examination of a sample of faeces. Chemical poisoning can often be diagnosed from a description of what the person has eaten, and from analysis of a sample of the suspect food. Mild cases can be treated at home. Lost fluids should be replaced by intake of plenty of clear fluids (see rehydration therapy). In severe cases, hospital treatment may be necessary. Except for botulism, and some cases of mushroom poisoning, most food poisoning is not serious, and recovery generally occurs within 3 days. However, some strains of can seriously damage red blood cells and cause kidney failure. (See also cholera; dysentery; typhoid fever.)