A number of practices hasten the development of antibiotic resistance, including over-prescribing by doctors, failure to follow the required dosage regime, and using the drugs to promote growth and reduce illness in livestock. These practices invariably speed up evolution by strongly selecting bugs resistant to antibiotics. The European Union has banned the use of antibiotics in animal feed, but it is still permitted in North America. According to the Union of Concerned Scientists, more than half of the antibiotics in the United States are used for agricultural purposes (which includes farming fish like salmon). This indiscriminate use of antibiotics can lead to resistant infections in humans in two ways. First, people can become infected with resistant bacteria by direct consumption of meat containing a resistant pathogen like Salmonella. The U.S. Food and Drug Administration estimates that every year up to 10,000 Americans develop antibiotic-resistant infections from eating chicken containing such bacteria. Second, resistant bacteria found in food animals can transfer resistance to normally harmless bacteria in humans through physical contact. These common bacteria are persistent and may spread from person to person. Occasionally, they can cause infections, and if the bacteria are resistant to antibiotics, the infections may prove difficult to treat.