These cases will be studied further to determine how the drug worked with their immune systems.

7. Are there other Ebola treatments out there?

Several experimental drugs are in development, but none has been effective in humans.

The market for these drugs is small -- Ebola is a rare disease, almost completely confined to poor countries -- so funding for drug development has come largely from government agencies.

In March, the NIH awarded a five-year, $28 million grant to establish a collaboration between researchers from 15 institutions who were working to fight Ebola. On Wednesday, Wellcome Trust and the United Kingdom's Department for International Development announced money for Ebola research will be made available from a $10.8 million initiative.

8. Will ZMapp or these other drugs be given to more Ebola patients?

An ethics panel convened by the World Health Organization concluded it is ethical to give experimental drugs during an outbreak as large as this one, but that doesn't mean it will happen.

Rolling out an untested drug during a massive outbreak would be very difficult, Doctors Without Borders says. Experimental drugs typically are not mass-produced, and tracking the success of such a drug, if used, would require extra medical staff where resources are already scarce.

In an opinion article published in the journal Nature this week, epidemiologist Oliver Brady says up to 30,000 people in West Africa would have so far required treatment in this outbreak if it was available.

9. What about an Ebola vaccine?

For the record, "vaccine" and "treatment" are not interchangeable terms. A vaccine is given to prevent infection, whereas treatment generally refers to a drug given to a patient who has developed symptoms.

There are several Ebola vaccines in development.

The Canadian government has donated between 800 and 1,000 doses of an experimental Ebola vaccine to WHO. The drug, called VSV-EBOV, is Canadian-made and owned, having been developed by the National Microbiology Laboratory.

It's never been tested on humans "but has shown promise in animal research," the agency says. We don't know if the vaccine has been given to anyone on the ground.

The NIH says a safety trial of an Ebola vaccine will start as early as September.