Chief Ebola doctor overseeing cases in Sierra Leone contracts the virus

(CNN) -- A doctor who has played a key role in fighting the Ebola outbreak in Sierra Leone is infected with the disease, according to that country's Ministry of Health.

Dr. Sheik Humarr Khan is being treated by the French aid group Medicins Sans Frontieres -- also known as Doctors Without Borders -- in Kailahun, Sierra Leone, Tim Shenk, an agency spokesman, told CNN.

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