The World Health Organization (WHO) has begun assessing more than 120 potential treatments for Ebola patients, it said on Friday, but so far has found none that definitely work, and some that definitely do not.

One drug used to treat HIV patients, lamivudine, had started to catch on as a potential Ebola treatment after one doctor used it and others followed, WHO scientist Martin Friede told a news conference.

But the WHO examined the evidence and found lamivudine had no effect on Ebola and should not be administered.

And despite the apparent success of ZMapp, the U.S.-made drug that grabbed headlines when two American aid workers with Ebola were given it and recovered, it has also not yet been proven to be effective, he added.

The apparent effect of ZMapp or other drugs that have been tried may simply be a result of the good care that the patients had received, or the fact that they were well-nourished before they fell sick, or because of other medicines, Friede said.

"Because these patients received multiple drugs - many of them received two, three or sometimes even four drugs - we cannot conclude anything," he said. "We can't conclude that the drugs work. That is the conclusion."

The medical charity Medecins Sans Frontieres plans to start trials next month of the drugs brincidofovir, from the U.S. firm Chimerix, and favipiravir, from Japan's Fujifilm, and to see how well blood plasma from Ebola survivors may work in curing those still infected.

Other potential treatments touted in the West African countries where Ebola has hit hardest include silver, selenium, green tea and Nescafé.

"It's understandable that the populations are willing to try anything, but there are a lot of charlatans out there who are trying to sell what in the old days would be called snake oil," Friede said.

The WHO aims to clarify things by pooling knowledge about the various potential treatments and publishing a list showing which ones should definitely be ruled out.