There had been no new cases since mid-May in two of the three areas hit by the disease - the initial outbreak zone of Bikoro and the city of Mbandaka, he said, describing the health response as showing "very strong progress".
On 4 June, an ethics committee in the Democratic Republic of the Congo (DRC) approved the use of five investigational therapeutics to treat Ebola, under the framework of compassionate use/expanded access.
Archbishop Fridolin Ambongo Besungu, co-adjutor archbishop of Kinshasa who previously served in the Diocese of Mbandaka-Bikoro, where the outbreak occurred, made a decision to suspend administering sacraments to protect churchgoers from contracting the disease.
Phase 1 of the vaccination campaign, a plan to protect urban centers and towns, has "gone well", said Salama.
Beginning with the 1976 discovery of Ebola in an area that is now the Democratic Republic of Congo, the country has experienced nine outbreaks.
"What this is telling us is the response (the WHO's vaccination program) is having an impact in those two locations", said Salama.
It is the capital of Equateur province, where the small town of Bikoro also is located.
An AP report Friday quoted DRC's health ministry saying another Ebola case had been confirmed even as the pace of new cases slows down. The newest confirmed case is in rural Iboko and is linked to a probable Ebola patient who died on 20 May, the ministry said. More than 98% of known contacts have been vaccinated, Salama said. It's the identification and follow-up of all people who may have come into contact with a person infected with the infectious disease.
The area had no infrastructure and could be covered only by motorbike, with several hours needed to trace every contact, he said.
Clinicians working in the treatment centres will make decisions on which drug to use as deemed helpful for their patients, and appropriate for the setting.
"We're cautiously optimistic but there's a lot of very tough work to do in phase two before we say that we're on the top of this outbreak", said Dr. Salama. "But we know to never underestimate Ebola".
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