(NBC News) A third American is battling Ebola.
Dr. Rick Sacra, a 51-year-old family physician from Massachusetts, contracted the deadly virus while treating patients in Liberia.
Friends say Sacra knew he was heading into an area in the midst of the worst Ebola outbreak in history, but like other missionaries he felt a calling to help.
"He came to me the day before he left, and I said to him, asked him, 'Do you know what you're getting yourself into?' And he said 'Yes, of course, but I have to go,'" recalls Dr. Gregory Culley.
Sacra is said to be in isolation and doing well.
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