John Bacon and Karen Weintraub

USA TODAY

The use of unproven drugs to combat the deadly Ebola virus won support Tuesday from the World Health Organization, which cited deep concerns over "the largest, most severe and most complex outbreak of Ebola virus disease in history."

The endorsement from the U.N.'s health care agency came after two American health care workers were treated with an experimental Ebola drug. Officials warned, however, that the improvement they showed may not have been directly related to the drugs.

WHO says 1,013 people have died since March in the outbreak, the vast majority of them in Liberia, Sierra Leone and Guinea. Officials estimate that Ebola kills about half of those afflicted with the disease.

"Over the past decade, research efforts have been invested into developing drugs and vaccines for Ebola virus disease. Some of these have shown promising results in the laboratory, but they have not yet been evaluated for safety," WHO said in a statement.

In a meeting Monday, a dozen experts from around the world – including ethicists, infectious disease experts, drug regulators and patient advocates – gave the green light to treating patients even as research continues.

A number of drugs to treat and vaccines to prevent Ebola have been produced by scientists around the world. But in what Marie-Paule Kieny, WHO Assistant Director-General, declared a "market failure," those approaches have not yet been tested in people.

"If it hadn't been for the investment of a few governments, we'd be nowhere," Kieny said in a press briefing Tuesday, praising the American and Canadian governments in particular for backing research. That research has stopped short of clinical trials in people, the most expensive part of the drug development process, which is generally handled by industry. With poor patients in poor countries, there is no obvious way for companies to make money on the drugs.

"This is why there are no stockpiles and we are not there yet. The only thing we can do now is accelerate the last stage of development and scale up production as quickly as possible," she said.

While studies in monkeys can suggest effectiveness and safety, it is impossible to know how people will respond until they are given a treatment, Kieny said.

The people who have been given an experimental Ebola therapy so far help prove her point.

According to published reports about their responses, an American man seems to have improved dramatically after the first dose, an American woman also improved, but only after the second dose, and a Spanish priest who was to receive a course of treatment died Tuesday. It's not clear whether the drug was responsible for his death, if the disease was too far along to be stopped, or even if he died before the first of three doses could be administered.

The experimental treatments are not necessarily a panacea, and WHO acknowledges they could be harmful. The Spanish missionary priest, Miguel Parajes, 75, died in a Madrid hospital, the hospital and his order said. The hospital would not confirm that he had been treated with the drug, but his order and Spain's Health Ministry said earlier that he would be.

The WHO panel determined that, if stringent ethical criteria are met, the drugs should be used.

"These (criteria) include transparency about all aspects of care, informed consent, freedom of choice, confidentiality, respect for the person, preservation of dignity and involvement of the community," WHO said.

WHO stressed that Ebola outbreaks can be contained using available interventions such as early detection and isolation, contact tracing and monitoring, and adherence to rigorous procedures of infection control.

However, the statement said there was "unanimous agreement that there is a moral duty to also evaluate these interventions (for treatment or prevention) in the best possible clinical trials under the circumstances in order to definitively prove their safety and efficacy or provide evidence to stop their utilization. Ongoing evaluation should guide future interventions."

The company that makes the drug that's been used so far, ZMapp, has agreed to send the few remaining courses of the three-dose treatment to Liberia to be used there.

It is still unclear how long it will take for companies to scale up production of drugs, but Kieny estimated it would likely be the end of the year before sufficient quantities would be available to begin small trials.

Safety trials of vaccines are likely to begin as soon as the next few weeks, she said, though it is unclear how soon they could be used to protect people in the affected West African countries: Liberia, Sierra Leone, Guinea and Nigeria. It has not yet been decided whether those vaccines would first be tried on health care workers putting themselves at risk to fight the disease, lab workers who diagnose it, or on people involved in burials who are exposed to the disease as they handle bodies, Kieny said. Some of these people have the means to protect themselves through infection control, so the vaccine may be more urgently needed elsewhere, she said.

The WHO will hold another panel meeting in a few weeks to discuss the ethics of how treatments should be distributed when they become available. At this point, Kieny said, there are too few doses for them to be distributed fairly.

The allocation of the first few doses to white people from rich countries presented an ethical problem, said Lawrence Gostin, university professor and director of the O'Neill Institute for National and Global Health Law at Georgetown University Law School.

"I think that this is very unfortunate for perceptions of global justice," Gostin said. Future doses should be distributed with the involvement of local governments, he said, as seems to be happening with the government of Liberia receiving the next doses of ZMapp.

Patient advocate Jeanine Thomas, who sits on the WHO ethics panel, said she thinks the treatment should also be given to patients, not reserved only for those treating the sick, as has been the case so far.

"I think it should be equal, patients and healthcare workers," said Thomas, president of the MRSA Survivors Network, a Chicago-based patient advocacy group.

The panel said "more detailed analysis and discussion" are needed to decide how to achieve fair distribution in communities and among countries, since there is an extremely limited supply of the experimental drugs and vaccines.

Also Tuesday, Liberian President Ellen Johnson Sirleaf suspended all travel by executive branch officials for one month. She also ordered those already abroad to return home within a week "or be considered as abandoning their jobs," according to a statement from her press secretary.

Most airlines flying in and out of the Liberian capital of Monrovia have suspended flights amid the unprecedented health crisis.