Volunteers search for needles and other drug paraphernalia along Church Street in Austin, Ind., in April. The region has recorded 142 new HIV cases since December, according to the state, in an outbreak tied to injected-opioid use. Seth Herald/Nurphoto/Corbis hide caption

itoggle caption Seth Herald/Nurphoto/Corbis

Needle exchange programs, like this one in Portland, Maine, offer free, sterile syringes and needles to drug users. The programs save money and lives, health officials say, by curtailing the spread of bloodborne infections, such as hepatitis and HIV. Robert F. Bukaty/AP hide caption

itoggle caption Robert F. Bukaty/AP

Truvada can dramatically reduce the risk of HIV infection when taken as a preventative medicine — if taken every day. Studies are underway to determine if young people are likely to take the pill consistently. Justin Sullivan/Getty Images hide caption

itoggle caption Justin Sullivan/Getty Images

A December celebration launching a partnership between members of the Garifuna community and a doctor in New York. The collaboration is aimed at reducing the HIV infection rate among the Garifuna. Alexandra Starr/NPR hide caption

itoggle caption Alexandra Starr/NPR

Augustine Goba (right) heads the laboratory at Kenema Government Hospital in Sierra Leone. He and colleagues analyzed the viral genetics in blood samples from 78 Ebola patients early in the epidemic. Stephen Gire/AP hide caption

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David Adam is a writer and editor at the journal Nature and was a special correspondent at the Guardian, writing about science, medicine and the environment. Courtesy of Farrar, Straus and Giroux, LLC hide caption

itoggle caption Courtesy of Farrar, Straus and Giroux, LLC

In Philadelphia, some drug users are selling clean needles from needle exchange programs on the street. Researchers say the black market isn't necessarily a bad thing. ImageZoo/Corbis hide caption

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Over a decade ago, rumors spread in South Africa that sex with a virgin could cure HIV/AIDS. In 2001, 150 people gathered in Cape Town to protest the rape of children and even babies, allegedly as a result of belief in this canard. Anna Zieminski/AFP/Getty Images hide caption

itoggle caption Anna Zieminski/AFP/Getty Images

Truvada has been around for a decade as a treatment for people who are already HIV-positive. In the last few years, it has also been shown to prevent new infections, and New York officials are embracing the pill as a way to prevent the spread of AIDS. Justin Sullivan/Getty Images hide caption

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Dr. Lisa Sterman held a Truvada pill at her office in San Francisco in 2012. She prescribed Truvada to patients at high risk for HIV infection even before the Food and Drug Administration approved the medicine explicitly for that purpose. Jeff Chiu/AP hide caption

itoggle caption Jeff Chiu/AP

Women in Bangalore, India, make red ribbons at an HIV support center in November 2012. Manjunath Kiran/AFP/Getty Images hide caption

itoggle caption Manjunath Kiran/AFP/Getty Images