ZMapp, an experimental treatment never before used on humans, may have saved the two American aid workers infected with the Ebola virus. Dr. Kent Brantly and Nancy Writebol have showed marked improvement since receiving the serum, which the National Institute of Health transported to Liberia last Thursday.

According to CNN, "within an hour of receiving the medication, Brantly's condition dramatically improved. He began breathing easier; the rash over his trunk faded away. One of his doctors described the events as 'miraculous.'" He is now being treated in the U.S., and Writebol is expected to arrive in the U.S. by tomorrow.

Ebola's fatality rate hovers around 90 percent, and over 700 people have died in West Africa during this latest crisis. But since ZMapp has not been approved for use in humans, and hasn't even gone through the clinical trials process, it's unlikely the serum will go into broader use.

[Image via AP]