Stacy Emminger holds the death certificate for her son, Anthony, who was addicted to heroin. His death was marked as a multidrug toxicity in Pennsylvania. Ben Allen/WITF hide caption

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Secretary of State John Kerry and African Union Commission Chairperson Nkosazana Dlamini Zuma signed an agreement Monday to establish the first Centers for Disease Control and Prevention in Africa. The U.S. will provide technical advice and a few staff for the agency. Alex Wong/Getty Images hide caption

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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

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Stringy particles of Ebola virus (blue) bud from a chronically infected cell (yellow-green) in this colorized, scanning electron micrograph. NIAID/Science Source hide caption

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Dr. Thomas Frieden, director of the U.S. Centers for Disease Control and Prevention, talks with Doctors Without Borders staff during a visit in August to an Ebola treatment center in Monrovia, Liberia. Tommy Trenchard for NPR hide caption

itoggle caption Tommy Trenchard for NPR

Ebola patient Amber Vinson arrived by ambulance at Emory University Hospital on Oct. 15. Now healthy, Vinson was discharged from the hospital Tuesday. Kevin C. Cox/Getty Images hide caption

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Dallas nurse Nina Pham speaks at a press conference after she was confirmed free of Ebola and released from a National Institutes of Health facility on Friday. Alex Wong/Getty Images hide caption

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At a CDC training session for clinicians headed to West Africa, a medical worker practices sanitizing hands after drawing blood from a mannequin portraying an Ebola patient. Brynn Anderson/AP hide caption

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When a high-risk patient is evacuated, strict precautions are followed. Above, aid workers and doctors in protective gear transfer Manuel Garcia Viejo, a Spanish priest diagnosed with Ebola, to a waiting ambulance at a Madrid airport. Spanish Defense Ministry/AP hide caption

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The entrance to the emergency room at Texas Health Presbyterian Hospital Dallas, where Thomas Eric Duncan was treated before he died from Ebola a week ago. Two health care workers who treated Duncan have tested positive for the disease. LM Otero/AP hide caption

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A plane arrives at New York's John F. Kennedy International Airport. Since Ebola screenings began Saturday, none of the 91 passengers identified as having an increased risk of an Ebola infection was found to be sick, the CDC says. Spencer Platt/Getty Images hide caption

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Passengers from three West African countries will face screening for Ebola symptoms when they arrive at John F. Kennedy International Airport in New York. Travelers are seen here at a JFK checkpoint earlier this week. Four other airports will begin screening next week. JUSTIN LANE/EPA /LANDOV hide caption

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A health official uses a thermometer on a passenger at the international airport in Lagos, Nigeria. Sunday Alamba/AP hide caption

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