Escherichia coli comes in a large number of strains, most of which live harmlessly in the guts of animals of all sizes. E. coli is actually a crucial part of the digestive process, but a few strains have developed negative traits which can lead to food borne illness. One of the most infamous forms of highly infectious E. coli is E. coli 0157:H7, a strain which was first identified in 1982, tied to an outbreak of illness from contaminated meat. In the United States, E. coli 0157:H7 is linked with 61 deaths and over 70,000 cases of food borne illness every year.
The sequence of letters and numbers in E. coli 0157:H7 refers to the specific classification of the organism, and differentiates it from other forms of E. Coli. This particular E. coli generates toxins which lead to stomach upset, causing diarrhea and vomiting. In the case of elderly, young, and immunocompromised individuals, E. coli 0157:H7 can cause hemolytic uremic syndrome, which will lead to kidney failure. E. coli 0157:H7 is an enterohemorrhagic form of the organism, which means that it is characterized by a bloody discharge, but rarely accompanied by a fever.
E. coli 0157:H7 comes from the gut of infected cattle and sheep, and the most common source of contamination is meat which has not been handled carefully in a slaughterhouse. However, the practice of concentrating manure in sewage lagoons which can rupture has led to contamination of groundwater and crop irrigation systems. As a result, E. coli 0157:H7 has been identified in swimming pools, drinking water, and a variety of crops grown low to the ground such as lettuce, spinach, and sprouts. E. coli 0157:H7 has also been known to appear in unpasteurized milk, orange juice, and raw eggs.
The roots of E. coli 0157:H7 appear to lie in changes in American farming practices. Ruminants which are fed on grain diets start to develop an acid imbalance in their normally neutral stomachs as a result of the rapid fermentation of grains in their rumens. This means that new bacteria adapted to the more acidic environment develop, and they can make the leap into the human digestive tract as well. Grass fed animals may carry bacteria as well, but the highly acidic environment of the human stomach kills the bacteria before it can cause an infection. The use of Concentrated Animal Feeding Operations to raise meat has been directly linked with the rise of E. coli 0157:H7 by numerous authorities, and the link between grain diets and the virulent bacteria was finally proved in 1998 and published by the United States Department of Agriculture.
The best way to avoid infection with E. coli 0157:H7 is to cook meat thoroughly and consume pasteurized dairy and juice products. If possible, consumers should seek out grass fed meats and dairy products to reduce the risk even further, and produce should always be carefully washed. Always keep raw meat separate from other foods, and wash surfaces that raw meat has been in contact with, including your hands, with hot water and soap. Use a meat thermometer to ensure that the meat has reached a safe temperature, which is at least 140 degrees Fahrenheit (60 Celsius) for rare meats, although 160 degrees Fahrenheit (71 degrees Celsius) is safer for beef and large cuts.