Food poisoning

Food-borne Illness or Food Poisoning, any illness associated with eating food contaminated by disease-causing bacteria, viruses, or parasites; natural toxins in plants and animals, such as mushrooms and shellfish; or harmful chemical agents such as insecticides and heavy metals. The symptoms of food-borne illness develop within a period of several hours to two days after eating contaminated food and usually include nausea, abdominal and stomach cramps, vomiting, and diarrhea. Dehydration (excessive fluid loss from the body) may develop, leading to thirst, dizziness, or fainting. As many as 76 million people suffer from food-borne illness in the United States each year, with about 5,000 of these cases proving fatal.

Although most cases of food-borne illness are generally mild and last for only a few hours, some forms may be life-threatening. A physician should always be consulted, particularly in cases involving infants and children, pregnant women, the elderly, and people with compromised immune systems, who are generally more susceptible to dehydration and other complications. In addition, suspect samples from a recent meal should be saved to help medical personnel determine the source of the illness.

CAUSES

Food-borne illness or food poisoning is commonly caused by certain bacteria or their toxins, which are poisonous proteins produced by these bacteria. One toxin-producing bacterium is Staphylococcus, which occurs almost everywhere and grows readily in foods stored at room temperature, especially processed meat and fish, milk, and cream-filled foods.

Escherichia coli, commonly known as E. coli, is a species of bacteria normally present in human intestines. A recently recognized strain, E. coli 0157:H7, produces high levels of toxins that can cause kidney damage, as well as septicemia, or blood poisoning. Symptoms can include diarrhea, chills, headaches, and high fever, and in some cases the infection can lead to death, even with medical intervention. Illness from E. coli may develop from consuming undercooked beef, unpasteurized milk, or from handling food without washing hands after changing diapers.

Botulism is a dangerous disease that results from eating improperly canned foods contaminated with toxins released by the bacteria Clostridium botulinum. Although commercial canning methods have made the occurrence of this disease relatively rare, home-canning practices in which food and the container are not thoroughly heated may result in botulism.

In some cases, food-borne illness is caused not by toxins but by rapidly growing colonies of the bacteria themselves. Among the most common of these harmful bacteria is Salmonella enteritidis, which is most often spread through poultry, eggs, and egg products such as mayonnaise. Eating undercooked poultry, using cooking utensils and cutting boards used for the preparation of raw poultry without properly cleaning them, and eating eggs or egg products that were not properly refrigerated are the primary causes of infection with Salmonella enteritidis.

Recently, scientists have discovered additional bacterial pathogens that can cause food-borne illness. Listeria monocytogenes, which can cause septicemia, meningitis, and stillbirth, kills up to one-third of the people infected and most often results from unsanitary commercial processing of dairy, poultry, and meat products—including pizza toppings. Campylobacter jejuni is now the most common bacterial cause of diarrhea in industrialized countries. Caused by contaminated raw foods, Campylobacter jejuni is the most prevalent pathogen in poultry, and in more serious cases can result in arthritis, septicemia, meningitis, inflammation of the heart and other organs, and Guillain-Barré syndrome (paralysis).

Chief among the viruses that cause food-borne illness is hepatitis A, which is excreted in the feces of infected individuals and reenters the food chain through unsanitary methods of food preparation. Water, salads, shellfish, and milk products are common sources of contamination. Hepatitis A infection causes a mild illness with symptoms that include fever, fatigue, nausea, loss of appetite, soreness in the abdominal area, and jaundice (accumulation of the pigment bilirubin in the blood, which causes yellowish discoloration of the skin and whites of the eyes). Other viruses include rotaviruses, which cause acute upset of the digestive system (gastroenteritis); and the Norwalk virus family, which also causes gastroenteritis.

Parasites, such as the Trichinella spiralis worm, can cause food-borne illness when humans eat meat from an infected host animal (see Trichinosis). In addition to initial gastrointestinal symptoms, parasitic infections can cause permanent damage to the eyes, heart, and other organs. Commercial food processing has greatly reduced the incidence of food-borne parasites; however, foods prepared under unsanitary processing conditions or at home—notably, cured or smoked meats—may harbor these pathogens.

Some mushrooms contain natural toxins that may be poisonous when eaten. Poisonous fungi of the Amanita species are the source of most mushroom poisonings, causing symptoms that range from mild stomach upset to death as a result of severe liver damage. Certain shellfish, such as mussels, clams, oysters, and scallops, become poisonous in the human digestive system if the shellfish have fed on toxin-producing planktonic algae. Similar algae-produced toxins may work their way up the food chain, becoming concentrated in large, predatory fish such as grouper or barracuda. Ciguatera fish poisoning occurs when people consume these fish. Sushi, when prepared from pufferfish flesh, may contain high levels of toxins if the fish’s internal organs—where toxins concentrate—are not carefully removed and discarded.

PREVENTION

Most food-borne illness may be prevented by observing strict sanitary measures in preparing and storing food, serving food soon after preparation, and quickly placing leftovers under refrigeration. Food processing techniques, from canning to irradiation (exposure of food to low levels of ionizing radiation), can protect consumers from food-borne illness as well (see Food Processing and Preservation).

Despite these safety features, public health officials and scientists warn that there is a growing risk of food-borne illness in the United States. Factors contributing to this risk include an increase in imported produce, often from developing countries with varying safety standards; a growing trend toward eating out, which leaves consumers more vulnerable to pathogens introduced by food handlers; and newly resistant and adaptive strains of bacteria that survive established food processing methods and appear in new food sources. Listeria monocytogenes, for example, survives both refrigeration and freezing; and E. coli and Salmonella enteritidis, commonly considered contaminants of meat and poultry, have recently been found in foods as varied as ice cream, apple cider, acidic fruit juices such as orange juice, melons, and lettuce. In 1995, federal and state officials began a nationwide effort to collect comprehensive and standardized data on food-borne illness in order to keep people informed and more effectively protected.