Doctors Without Borders says that human testing on a potential Ebola drug is being stopped because there aren't enough patients because of a decline in Ebola cases.

The drop-off in Ebola infections is good news for Liberia, but it means there are not enough sick people to take part in the study.

The announcement Wednesday by Doctors Without Borders comes days after the drug's manufacturer said it would no longer take part.

The drug brincidofovir has been used to treat other viruses and doctors wanted to study whether it could also cure Ebola. There is no licensed treatment for the disease that has killed about 9,000 people in West Africa over the past year.

On Monday, human testing got under way in Liberia for two potential vaccines to prevent Ebola.