An X-ray of the chest of a man with tuberculosis. The areas infected with TB bacteria are colored red. Science Photo Library/Corbis hide caption

itoggle caption Science Photo Library/Corbis

New York City Mayor Bill de Blasio talked about Dr. Craig Spencer last month at a news conference, and has another one set for Tuesday which Spencer will attend, Ebola-free. Andrew Burton/Getty Images hide caption

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Mary Mallon, known as "Typhoid Mary," was immune to the typhoid she carried. Working as a cook, she spread the disease in New York and ended up quarantined on Brother Island (above) for more than two decades. Bettmann/Corbis hide caption

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Don't look for leading Ebola researchers at the Sheraton New Orleans. Louisiana health officials told doctors and scientists who have been in West Africa not to come to a medical meeting in town. Prayitno/Flickr hide caption

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An Ebola health alert is displayed at the entrance to Bellevue Hospital in New York City, where Dr. Craig Spencer was quarantined after showing symptoms consistent with the virus. Bryan Thomas/Getty Images hide caption

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New Jersey Governor Chris Christie (right) and New York Governor Andrew Cuomo both insist on mandatory quarantine for healthcare workers who've had contact with Ebola patients. Christie wants them held in a medical facility; Cuomo says a home quarantine with outside monitoring would do. Mark Lennihan/AP hide caption

itoggle caption Mark Lennihan/AP

New York Gov. Andrew Cuomo, left, listens Friday as New Jersey Gov. Chris Christie talks at a news conference in New York. The governors announced a mandatory quarantine for people returning to the United States through airports in New York and New Jersey who are deemed to be at "high risk" for Ebola. Mark Lennihan/AP hide caption

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A private security guard patrols the apartment building in Dallas where Ebola patient Thomas Duncan stayed. The family that hosted him is quarantined. Tom Pennington/Getty Images hide caption

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Eva Nah raised her nephew Shacki from the age of 2, when he lost his parents. "Every day [when] I wake up I cry because I feel bad that Shacki has left me," she says. Tommy Trenchard for NPR hide caption

itoggle caption Tommy Trenchard for NPR

Information minister Lewis Brown is proud of Liberia's strong response to Ebola but admits, "We think sometimes we could have done better — much quicker — to improve the response time." Tommy Trenchard for NPR hide caption

itoggle caption Tommy Trenchard for NPR

The two American Ebola patients are being cared for separately in rooms like this in the special isolation unit, known officially as the Serious Communicable Disease Unit, at Emory University Hospital. Emory University Hospital hide caption

itoggle caption Emory University Hospital