Three top secret, experimental vials stored at subzero temperatures were flown into Liberia last week in a last-ditch effort to save two American missionary workers who had contracted Ebola, according to a source familiar with details of the treatment. On July 22, Dr. Kent Brantly woke up feeling feverish. Fearing the worst, Brantly immediately isolated himself. Nancy Writebol's symptoms started three days later. A rapid field blood test confirmed the infection in both of them after they had become ill with fever, vomiting and diarrhea.

It's believed both Brantly and Writebol, who worked with the aid organization Samaritan's Purse, contracted Ebola from another health care worker at their hospital in Liberia, although the official Centers for Disease Control and Prevention case investigation has yet to be released.

A representative from the National Institutes of Health contacted Samaritan's Purse in Liberia and offered the experimental treatment, known as ZMapp, for the two patients, according to the source.

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