Small wonder that antibiotics are becoming less potent: a new government survey has estimated that 50 percent of all prescriptions for oral antibiotics were unnecessary and that in 2010, the year studied, doctors were prescribing these drugs for 833 of every 1,000 Americans – that works out to prescriptions for four out of five persons per year. The survey, from the U.S. Centers for Disease Control and Prevention (CDC), showed that antibiotic use is highest in the South and Appalachia and that nationwide prescription rates were higher for young kids (those under 10) and seniors 65 or older. The lowest prescription rates were in the west, 639 per 1,000 persons. This escalating rate of prescriptions is a major contributing factor in the evolution of microbes to resist the drugs, making the diseases these bugs cause harder to treat, the CDC authors wrote. The survey showed that the most frequently prescribed antibiotic agent was azithromycin, often used to treat bronchitis. A glaring problem is that bronchitis is usually is caused by a virus, and antibiotics, including azithromycin, are ineffective against viruses.