Can Ebola Victims Survive Without ZMapp? Well, It's Complicated

The first person to be diagnosed with Ebola within the United States, Thomas Eric Duncan, is currently receiving treatment at a North Texas hospital; meanwhile, U.S. health officials are quickly trying to quarantine anybody who came in contact with the victim. But how will Duncan and other potential Ebola patients survive without ZMapp, the only (somewhat) approved experimental drug to treat the virus? Federal officials are trying to increase the production of the treatment for patients in both the U.S. and West Africa, but Duncan, at least, won't be treated with ZMapp — because the U.S. has run out.

ZMapp has yet to be tested on humans and officially approved for usage. However, the World Health Organization issued the use of ZMapp in August, saying it's ethical to use the untested drug if it could indeed save lives. The experimental drug was used on Dr. Kent Brantly and humanitarian health worker Nancy Writebol in August when they were transferred from West Africa to Atlanta, Georgia, after being diagnosed with the deadly virus. Both made full recoveries.

Unfortunately, there was only a small supply of ZMapp at the time, and health officials said it could take months to produce more. Because the meager supply of ZMapp was already depleted when Duncan was diagnosed last week, he won't be treated with ZMapp.

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Does that mean Duncan's rate of survival is automatically lower than Brantly's and Writebol's? Not necessarily. Although Brantly and Writebol were able to beat the virus after receiving ZMapp, health researchers say it's still too early to tell if the experimental drug was directly responsible for their survival.

Thomas Geisbert, a virologist studying Ebola at the University of Texas Medical Branch, told ABC News in late August that while researchers have faith in ZMapp, there are other reasons why people survive Ebola. Some victims may have stronger immune systems or a smaller viral load, Geisbert said. He added that there's definitely "something to be gained from understanding why certain people survive."

There's also the case fatality rate to take into account. According to the World Health Organization, the average Ebola fatality rate is 50 percent, though previous outbreaks have ranged between 25 percent to 90 percent. The Centers for Disease Control and Prevention have said that current fatality rate of the 2014 West Africa outbreak is around 55 percent.

While that percentage may be high, Dr. Bruce Ribner, medical director of the infectious disease unit at Emory University Hospital and one of the doctors who treated Brantly and Writebol, said at a press conference in August that Ebola can be beaten — with the right tools. This doesn't always mean ZMapp, but also a ton of IV fluids replenishing electrolytes and potassium in a patient's body:

One guidance we are giving back to our colleagues is that they need to pay attention to replacing these electrolytes. Even if they’re unable to do the same tests, there are things they can do to try to improve outcomes.

Ribner added that Brantly and Writebol had a better nutritional diet than Ebola victims in West Africa, which may have attributed to their survival.

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Still, the extremely small sample size of ZMapp patients has shown that there's more of a chance of survival with ZMapp than none at all. According to The New York Times, of the seven Ebola victims treated with ZMapp, five survived; one of the two deceased victims also had diabetes and hypertension, but was reportedly showing improvement after receiving dosage.

But as far as experiments go, the only substantial evidence researchers currently have about ZMapp's survival rate is a recent experiment with monkeys, published in the science journal Nature. Of the monkeys that were given ZMapp, 100 percent were completely cured. The three monkeys that didn't receive the drug died barely a week after infection.

While researchers point this study as hope for ZMapp, the precise chance of survival without the drug is still a medical mystery.