Here's why the experimental Ebola drug can't be used by everyone

A CDC official stands under a map showing the agency's deployment of workers in West Africa at the agency's Emergency Operations Center, Tuesday, Aug. 5, 2014, in Atlanta. (AP Photo/David Goldman)

Two Americans suffering from Ebola have been treated with an experimental drug, and they've reportedly seen big improvements. Is it time to try sending ZMapp to West Africa to aid the hundreds suffering from the disease? No, experts tell the Los Angeles Times.

Drugs require extensive testing in order to determine whether they do their job safely, and offering ZMapp for widespread use could prevent researchers from making that judgement.

"There's a fairly good chance that it could do more harm than good," an expert says, adding that some patients who could have survived on their own might end up dying if they use the drug.

If the two Americans survive, the Times notes that ultimately the only "certainty is that the drug didn't kill them." While Ebola is believed to be fatal in 45% to 90% of cases, the Times notes, certain traits appear to be associated with a higher chance of survival, LiveScience reports.

One is a tougher immune system that can handle damage to cells called CD4 and CD8 lymphocytes. Those with certain types of a gene called human leukocyte antigen-B—related to immune function—may also have a better shot against the disease.

And a mutation in the gene known as NPC1 may make people resistant to the disease in the first place. Click for the latest.