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The posterior end of the Loa loa worm is visible on the left. The disease-causing worm can now be located with a smartphone/microscope hookup. That's a big help because a drug to treat river blindness can be risky if the patient is carrying the worm. BSIP/UIG via Getty Images hide caption

itoggle caption BSIP/UIG via Getty Images

Bob Skierski at the beach in Avalon, N.J., just hours before he fell ill and went to the hospital. He never went home. Courtesy of Jennifer Rodgers hide caption

itoggle caption Courtesy of Jennifer Rodgers

Rod-shaped specimens of Yersinia pestis, the bacterial cause of plague, find a happy home here in the foregut of a flea. Fleas can transmit the infection to animals and people, who can get pneumonic plague and transmit the infection through a cough or kiss. Science Source hide caption

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A man stands near collapsed houses in Bhaktapur, on the outskirts of Kathmandu, on April 27, two days after a magnitude-7.8 earthquake hit Nepal. Aftershocks tend to get less frequent with time, scientists say, but not necessarily gentler. Prakash Mathema/AFP/Getty Images hide caption

itoggle caption Prakash Mathema/AFP/Getty Images

Sequencing the genes of a cancer cell turns up lots of genetic mutations — but some of them are harmless. The goal is to figure out which mutations are the troublemakers. Kevin Curtis/Science Source hide caption

itoggle caption Kevin Curtis/Science Source

The blood cancer in soft-shell clams poses no risk to humans, but it does kill the shellfish. Pat Wellenbach/AP hide caption

itoggle caption Pat Wellenbach/AP

For someone 2.5 inches shorter than average, the risk of coronary artery disease increases by about 13.5 percent, scientists found. PW Illustration/Ikon Images/Corbis hide caption

itoggle caption PW Illustration/Ikon Images/Corbis

There's a widely held assumption that a slight imbalance in male births has its start at the very moment of conception. But researchers say factors later in pregnancy are more likely to explain the phenomenon. CNRI/Science Source hide caption

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Glenn Lightner in 2012 at age 13. His father searched clinicaltrials.gov for years, to no avail, hoping to find a promising experimental cancer treatment that might save his son's life. Courtesy of Lawrence Lightner hide caption

itoggle caption Courtesy of Lawrence Lightner

It's a good start when experimental compounds stop the proliferation of cancer cells in the lab. But, as many researchers have learned the hard way, that's just an early step toward creating a worthwhile treatment. Science Source hide caption

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Tobacco smokers are more likely than nonsmokers to die from infection, kidney disease and, maybe, breast cancer. iStockphoto hide caption

itoggle caption iStockphoto