In a major breakthrough, doctors have claimed that an experimental drug shows some early, encouraging signs of effectiveness in its first human test against Ebola.

The tests of the drug favipiravir conducted in West Africa on 69 adults and teens were released on Monday and showed survival rates of 85% among those who were administered the drug when virus levels were comparatively low.

This is slightly higher than the 70% patients who survived after using the drug earlier.

More people need to be tested with control groups to arrive at a conclusion on the drug, researchers said at the Retrovirus Conference in Seattle.

The drug made no difference on those who got it later.

Unfortunately, most patients seek care after five days since catching the virus, when the symptoms were pronounced and the infection well established.

"We have preliminary evidence" that favipiravir may be effective, says a statement by Carlos Moedas, European commissioner for Research, Science and Innovation, that helped fund the work.

"If these results are confirmed by the ongoing clinical trial, it will be the first-ever treatment to be deployed against this deadly disease during the current outbreak."

The current Ebola outbreak has seen nearly 23,000 cases and around 9,000 deaths, mostly in Liberia, Guinea and Sierra Leone.

favipiravir, also known by its brand name, Avigan, is made by a Japanese company, Toyama Chemical. It was approved in Japan last year for treating flu and tests suggest it also may work against other viruses, reports AP.

A French nurse who got Ebola while volunteering in Africa for Doctors Without Borders was treated with favipiravir and she recovered.

The new study was launched in December in two Ebola treatment units in Guinea run by the aid group.

Others involved in the study include the aid group Alliance for International Medical Action and Inserm, the French public health agency.

Survival has improved with time as cases are detected and treated earlier, and more care is available.

In December, doctors reported that survival among nearly 600 recent Ebola patients in Sierra Leone was about 70%, compared to only about 26% when the outbreak occurred.

Among those treated more recently, survival was over 76%.

However, transmission remains "widespread" in Sierra Leone, according to WHO.