New Delhi, June 6 -- He walked out of Charite hospital on Saturday with his wife and four children, seventeen days after being admitted in isolation with one of the rarest and most dangerous strains of the Ebola virus the world has seen this century. Dr. Peter Stafford, a 39-year-old American missionary surgeon, did not know he had Ebola when he performed the operation that infected him. Nobody did.

something a surgeon sees and operates on. The woman died the next day. She was buried before a test could be run. It was only afterward, when the Bundibugyo ebolavirus outbreak was officially declared on May 15, that the pieces came together. Stafford had likely been exposed to the virus through bodily fluids during surgery, without knowing w...