As the Ebola outbreak in West Africa worsens, researchers in the U.S. are reporting promising results of vaccines and treatments in monkeys infected with the deadly virus. However, according to Dr. Anthony Fauci of the National Institutes of Health, the vaccine he and his team is working on will not be tested in humans until next month. Right now, however, a major public health question looms: Should candidate vaccines and treatments be rushed into use, given the current epidemic situation?

Hope in controlling the worsening Ebola epidemic is waning, and the numbers of infections and deaths have increased, including among health care providers. Top physicians in both Guinea and Sierra Leone have succumbed to their Ebola illnesses contracted while trying to manage the viral outbreak.

There are currently close to 1,400 people with Ebola infections for which there are no cure. No vaccines or other preventive drugs for warding off the Ebola virus exist.

There are several major barriers to research on Ebola countermeasures. Foremost, Ebola is rare and deadly so it is not possible to design a clinical trial in which some trial participants are infected with the virus. Testing can only be done in animals or in humans accidentally infected with the virus.

Another hurdle in prevention research is that because Ebola is rare, there is no monetary incentive. Potential sales are unlikely able to offset the costs of research and development.

Finally, the mortality for patients of Ebola illness is high and rapid. As many as 90 percent of infected individuals typically die. Administering experimental treatments and preventives in a high-mortality outbreak is risky. If a patient on an experimental treatment dies, the treatment itself is at best said to fail and at worst said to have caused the death. If a patient survives, then it is impossible to know whether the patient would have survived without the experimental intervention.

“To bring a strictly experimental approach to this population – most people think that’s not a good idea, and not doable,” says Dr. Heinz Feldmann, chief of the laboratory of virology at the National Institute of Allergy and Infectious Diseases.