The two Americans infected with the Ebola virus, Kent Brantly and Nancy Writebol, have received a dose of the experimental Ebola serum with encouraging results. The serum, however, has not been approved by the FDA or even tested on humans.
The drug, called Z-Mapp, was developed by Mapp Biopharmaceuticals. It is one of the first treatments to show promise fighting the disease, and it works by preventing the Ebola virus from infecting new cells. Though it's ostensibly illegal to administer an untested drug, this situation would likely fall under the FDA's "compassionate use" exception to treat patients with immediately life-threatening conditions.