Another American doctor infected with Ebola, charity says

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Another American missionary doctor has tested positive for Ebola, an aid group said Tuesday.

SIM USA said the doctor, who was not identified, was treating obstetric patients at ELWA hospital in Monrovia and had not treated Ebola patients in the hospital's isolation unit, which is separate from the main hospital. The charity said it was not yet known how the doctor was infected, but he immediately isolated himself when he showed symptoms.

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The new case comes two weeks after Dr. Kent Brantly and his colleague Nancy Writebol, who worked for SIM, walked out of an Atlanta hospital virus-free after being infected and evacuated from Liberia.

The doctor was transferred to the Ebola isolation unit and is doing well and in good spirits, SIM said in a statement. The group planned a briefing later Tuesday.

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"My heart was deeply saddened, but my faith was not shaken, when I learned another of our missionary doctors contracted Ebola," said Bruce Johnson, president of SIM USA. "As a global mission, we are surrounding our missionary with prayer, as well as our Liberian SIM/ELWA colleagues, who continue fighting the Ebola epidemic in Liberia."

—By Lisa Tolin, NBC News.

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