However, they told VOA this week that dangers remain as hundreds of international and local workers battle the outbreak in the Democratic Republic of the Congo.
"Yes, we are confident we can eventually contain this outbreak," said Dr. Peter Salama, the WHO's head of emergency response, but questions about speed and logistics remain. "Remember, we're talking about very remote rural villages surrounded by hundreds of kilometers of forested area."
One encouraging sign is that epidemiologists have tracked the origins of the outbreak in rural DRC, said Dr. Hilde de Clerck, who is part of the aid group's response command center in Brussels.
"It's definitely too early to say it's under control, but it seems rather positive," she said Thursday. The epidemiologists have tracked what she called the transmission tree, locating the patients and their families, which gives scientists a good overview of the origins of the outbreak and how it has spread.
"It's a good sign that we have this vision, and it's also a good sign that our teams seem to say these people seem linked," and confined to a few families and a few villages.
This outbreak raised fears that it could spread like the West Africa epidemic in 2014-16, which killed more than 11,000 people in Guinea, Liberia and Sierra Leone. That was the worst outbreak in the known history of the disease.
De Clerck said it was not a surprise that the current outbreak seemed to be moving slowly. Rural outbreaks in the DRC generally are contained fairly quickly because villages are isolated and people are not likely to travel to other areas.
In the West African outbreak, which started in Guinea, better roads and the willingness of people to travel to other towns allowed the virus to spread more quickly, she said.
Other factors also are in play, Salama said Thursday. Reforms in the WHO emergency response program over the past few years allowed a very rapid reaction to the outbreak, he said. In addition, other aid agencies mobilized quickly. MSF was able to deploy a Congolese team from Kinshasa immediately to the first village where the disease was suspected.
What's more, this time, a vaccine program has been used from the start. "We didn't have a possibility of using an Ebola vaccine in previous outbreaks," Salama said.
Medical teams are using a process called ring vaccination with a new drug developed by the company Merck. "We find a confirmed case, and then vaccinate all the close contacts of that case and then the contacts of those contacts," he said.
The immunization program may be key to halting the spread of the virus in Mbandaka, the capital of Equiteur province. Four cases were confirmed in the city of more than 1 million people, raising fears of a wider spread, as the city sits on the Congo River, which connects to Kinshasa and Brazzaville in the Republic of Congo.
However, Salama said, teams have vaccinated about 500 contacts of the Mbandaka cases, and it appears the virus hasn't spread in the city.
"Still we should be vigilant for the city, because indeed Mbandaka is a big city and the River Congo is not far, with indeed the boats on the river. But the good news for now is that Mbandaka reports extremely few cases and they seem all linked one to the other," de Clerck said.
With any outbreak, de Clerck said, medical teams must build trust in communities, especially with something like Ebola, which has a high mortality rate.
"People are very often afraid, or sometimes people think it could be witchcraft or something that is causing those deaths. So we have health promoters on the field to explain to people what is going on and encouraging people actually to come to the health structures," she said.
Respect for residents, traditions
Health teams need to respect communities and traditions. For instance, she said, it's not necessary to quarantine contacts of Ebola patients. People are not contagious if they don't show symptoms, she said. MSF encourages contacts of patients to continue their daily lives, but to check in frequently with medical providers.
And when people do fall ill, the best treatment centers don't bar visitors. "People are isolated, but we always say an isolation is not a prison. You need to have patient terraces, you need to have windows and people can talk over the windows, over the terraces to their family members, to their neighbors," as long as visitors stay at least two meters away from patients and don't touch them, she said.
In the burials of Ebola victims, there can be compromises to allow mourners to follow some traditions safely. It takes more time, de Clerck said, to do such things as allowing a family member to wear a protective suit to help prepare a loved one's body for burial, or to arrange ways for mourners to gather safely, but it's possible.
There is a need for promptness in treatment and burial, "but you cannot destroy all traditions, because people will not trust you ... and they will refuse to participate or to follow your advice. It's way better to have the community on your side," she said.