Studies show that having too many tests done too frequently is a recipe for getting sick, not staying healthy. Medicimage/Science Source hide caption

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Magnified 25,000 times, this digitally colorized scanning electron micrograph shows Ebola virus particles (green) budding from an infected cell (blue). CDC/NIAD hide caption

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Doctors used a rapid DNA test to identify a Wisconsin teen's unusual infection with Leptospira bacteria (yellow), which are common in the tropics. CDC/Rob Weyant hide caption

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After genetic testing revealed a heightened risk for breast cancer, Angelina Jolie had a precautionary double mastectomy. Alastair Grant/AP hide caption

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Disease susceptibility varies among ethnic groups, but medicine hasn't always recognized that. Jo Unruh/iStockphoto hide caption

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Stacy Riggs of Fairfax, Va., is prepped for a screening for atrial fibrillation by Life Line Screening medical assistant Kennea Blake at Messiah United Methodist Church in Springfield, Va. Jenny Gold/Kaiser Health News hide caption

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A broken hip like the one at left is a big health worry for older women. hide caption

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Anne Jones, 62, and Robin Jones, 73, at their home in Menlo Park, Calif. He took a test that revealed proteins typical of Alzheimer's disease. Ramin Rahimian for NPR hide caption

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