MONROVIA, Liberia—Helena Henry watched Ebola take her mother, two brothers, a grandmother and sister-in-law. So when she survived her own bout with the virus, the 30-year-old seller of secondhand clothes hoped it couldn’t infect anyone close to her again.

On the night she was discharged from a clinic outside the Liberian capital Monrovia where she had been treated for the virus, she returned to her fiancé and companion of 12 years and celebrated. They slept together, she said. Less than a week later, he became ill.

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