NEW YORK — The number of suspected cases of Ebola has risen to 18 from nine in nearly a week in an isolated part of Democratic Republic of Congo, where three have died from the disease since April 22, the World Health Organization said Thursday.
The WHO was criticized for responding too slowly to an outbreak in West Africa in 2014 that left more than 11,000 people dead, and Dr. Peter Salama, the executive director of the organization’s health emergencies program, said at a briefing it was essential to “never, ever underestimate Ebola’’ and to “make sure we have a no-regrets approach to this outbreak.’’
The risk from the outbreak is “high at the national level,’’ the WHO said, because the disease was so severe and was spreading in a remote area in northeastern Congo with “suboptimal surveillance’’ and limited access to health care.
“Risk at the regional level is moderate due to the proximity of international borders and the recent influx of refugees from Central African Republic,’’ the organization said, but it nonetheless described the global risk as low because the area is so remote.
About a week ago, in addition to the nine suspected cases, 125 patients who had come into close contact with the disease were being monitored. Now, about 400 patients are being followed, and the two newest possible cases were reported Monday and Tuesday, according to the latest report on the WHO website.
The Ebola virus causes fever, bleeding, vomiting, and diarrhea, and it spreads easily by contact with bodily fluids. The death rate is high, often surpassing 50 percent, particularly with the Zaire strain, which has been confirmed in two cases in this outbreak.
The outbreak was reported in a densely forested part of Bas-Uele province, near the border with the Central African Republic. Cases have occurred in four separate parts of a region called the Likati health zone.
Aid groups and the WHO have struggled to reach the affected area, which has no paved roads and can be reached only by a motorcycle ride through the forest or by helicopter or light aircraft.
The first known case occurred on April 22, when a 39-year-old man who had fever, vomiting, diarrhea, and bleeding died on the way to a hospital in the Likati zone. The person caring for him and a motorcyclist who transported him also died.
The first six months of the response to the outbreak are expected to cost the WHO and aid groups $10 million, Salama said at the briefing. He said telecommunications networks would have to be established and airstrips repaired so that aid workers can provide the necessary medical care.
The WHO, aid groups, and the Congolese government are discussing the possibility of using an experimental Ebola vaccine, made by the US pharmaceutical company Merck, that proved effective in Guinea.
The response would involve a “ring vaccination,’’ in which contacts of patients, contacts of contacts, and health workers would be vaccinated. There would be no mass public vaccination.
The vaccine has not yet been licensed, and its use would require permission on several fronts. Nonetheless, Salama said that if permission were granted, the vaccine could be made available in a week or so. Other experimental antiviral drugs may also be considered.
The Ebola virus is considered endemic in the Democratic Republic of Congo, where eight outbreaks, the largest involving about 300 patients, have been recorded since 1976.
The country “has considerable experience and capacity in confronting these outbreaks,’’ Dr. Daniel Bausch, an Ebola expert at the WHO, said in an e-mail. He added, “I think there is a very good probability that control can be rapidly achieved.’’
Salama said that aid workers had reached a town in the Likati zone, which was as close as they had been able to come to the epicenter of the outbreak. He said aid groups were setting up centers for treatment and isolation and mobile labs.
