Liberia said it planned to treat two infected doctors with an unproven Ebola medicine called ZMapp. They would become the first Africans to receive the drug, which has been given to a Spanish priest who later died and two U.S. aid workers.
The outbreak is the world's largest and deadliest and the U.N. agency last week declared it an international health emergency. The WHO has appealed for funds and medical staff to supplement health care in one of the poorest regions in the world.
So far, 1,013 people have died, the vast majority in Guinea, Liberia and Sierra Leone. Two have died in Nigeria.
The suffering has been exacerbated by health services that are struggling to cope.
On Tuesday, Liberian Ceceilia Gbelley lay on the grass among a group of seven outside an Ebola treatment centre at Monrovia's Elwa hospital because there was no space for them inside. All said they feared they might have the disease.
"I'm very weak. My chest is burning," said Gbelley, who had nursed her aunt while she vomited blood and showed other symptoms of the virus. The aunt died and Gbelley then fell ill. She said she rode to the hospital in a shared taxi.
In a sign of the desperation for even experimental medicine as the death toll mounts, Twitter users in West Africa, where Ebola is killing around 60 percent of patients who become infected, created the #GiveUsTheSerum hashtag.
There are no licensed treatments or vaccines for Ebola, a contagious haemorrhagic disease, but several biotech companies and research teams have been working on potential drugs.
The WHO's panel of medical ethicists said several experimental drugs had passed the laboratory and animal study phases of development and should be fast-tracked into clinical trials and made available for compassionate use.
"There was unanimous agreement among the experts that in the special circumstances of this Ebola outbreak it is ethical to offer unregistered interventions as potential treatments or prevention," the WHO's assistant director general Marie-Paule Kieny said after an ethics panel published its guidance.
The WHO meeting was called after ZMapp, made by U.S. biotech company Mapp Biopharmaceutical, was given to the two U.S. aid workers infected in Liberia. Kieny said she had heard reports that the treatment had a swift and dramatic effect on them.
WHO said only around 10 to 12 doses of the drug have been made. Liberia was preparing to treat the two Liberian doctors with ZMapp after U.S. authorities approved its export.
On Tuesday, Canadian Health Minister Rona Ambrose said Canada would donate 800 to 1,000 doses of an experimental Ebola vaccine developed in its government lab to the WHO for use in West Africa.
"Our government is committed to doing everything we can to support our international partners, including providing staff to assist with the outbreak response, funding and access to our experimental vaccine," Ambrose said in a statement.
Canada owns a small quantity of the vaccine and would need four to six months to make a large quantity.
The 75-year-old priest, who the Health Ministry said was also being treated with ZMapp, died in hospital in Madrid on Tuesday. He contracted Ebola in Liberia while working for a non-governmental organisation. It was unclear whether his death shed any light on the efficacy of the drug.
Despite the stir caused by ZMapp, the WHO has said preventive public health measures are crucial to curbing the outbreak.
"Decisions to seal off the hot zone of disease transmission, that is, the area where the borders of Guinea, Liberia, and Sierra Leone intersect, are critical for stopping the reinfection of areas via the cross-border movement of people," WHO director-general Margaret Chan said in Geneva.
The ethics panel said it was likely the first tests of these drugs in humans would be conducted over the next two to four months, but cautioned that even after that, and if the trials proved successful, supplies would be limited.
Companies with possible treatments include Tekmira Pharmaceuticals, Biocryst Pharmaceuticals and Siga Technologies.
GlaxoSmithKline and U.S. scientists at the National Institute of Allergy and Infectious Diseases hope to start a clinical trial of an experimental Ebola vaccine as soon as next month, after promising test results in primates.
Another experimental vaccine from Johnson & Johnson's Crucell unit should enter Phase I clinical trials in late 2015 or early 2016, while Profectus Biosciences is also working with U.S. scientists on another preclinical vaccine.
But with the long lead times and no sign of an end to the outbreak, authorities have been taking their own emergency measures to try to contain it.
Ivory Coast, the economic powerhouse of French-speaking West Africa, on Monday banned air travellers from the three worst-hit countries and ordered its flagship carrier Air Cote d'Ivoire to cease flights to and from them.
Ivory Coast has not registered any cases but is seen as vulnerable given its shared borders with Guinea and Liberia.
Ghana's government said the start of the academic year would be delayed for at least two weeks for all tertiary institutions to allow Ebola screening measures to be put in place.
Guinea and Sierra Leone have been ordered by the Confederation of African Football to move their African Nations Cup soccer qualifiers next month.