The virus causing this outbreak, called Bundibugyo, is less common than others that cause Ebola disease and there are no specific treatments or vaccines for it. Already more than 1,400 people have been diagnosed and 438 have died, the head of the World Health Organization, Tedros Adhanom Ghebreyesus, said Thursday.

The WHO announced the same day that the first participant had been enrolled in the study, which is evaluating whether the antiviral remdesivir, the experimental antibody treatment MBP134, or a combination of both can improve survival among patients infected with the Bundibugyo virus.

Survival will be tracked for 28 days after starting treatment, according to WHO research adviser Dr. Vasee Moorthy.