The UN has endorsed the use of unproven drugs to combat the current Ebola outbreak.

The World Health Organization has identified this outbreak as the largest and most severe outbreak of Ebola virus in history.

This endorsement comes after two Americans who contracted Ebola were given an experimental serum and are now recovering. Health officials caution, however, that the improvement is not necessarily the result of the drugs.

The Ebola death toll is now more than 1,000 people.

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

There have been many drugs and vaccines for Ebola, but the drugs have typically stopped short of clinical trials as a result of "market failure" said Marie-Paule Kieny, WHO Assistant Director-General.

Kieny said most of the time, the development of the drugs stopped because clinical trials are the most expensive stage of the drug development process and in poor patients in poor countries, there is really no way for companies to make money off the drugs once they are approved.

She also said there is no way to know how people will respond to the experimental drugs even though studies using monkeys have suggested that the drugs are safe and effective.

There is also no way to know whether the drugs are safe. Using the experimental drug that helped the two Americans diagnosed with Ebola, a Spanish priest who possibly received a course of the treatment died Tuesday. Researchers are unsure as to how he died and if his death is related to the treatment.

WHO said as long as ethical criteria is met, the drugs should be used to combat this outbreak.

"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.

The experimental drug used to treat two Americans was created by ZMapp. The company agreed to send the few remaining doses of the treatment to Liberia to be used there.

Kieny also said that safety trials of vaccines could begin in the next few weeks, but they are unsure about how soon the vaccines could be used on people.

Currently there are ethical arguments about how moral it was to distribute the few doses to white people from rich countries and to healthcare workers.