The UN said 14 cases of the deadly virus had been confirmed between April 4 and May 15 since the outbreak in remote Bikoro, in northwestern Equateur province.
One confirmed case of the virus was registered in Mbandaka, a little under 100 miles (160 kilometers) from the town of Bikoro, on Thursday, prompting the WHO to convene a meeting of experts in Geneva.
"The confirmed case in Mbandaka, a large urban center located on major national and international river, road and domestic air routes, increases the risk of spread within the Democratic Republic of Congo and to neighboring countries," the WHO said.
Learned from the pastDR Congo Health Minister Oly Ilunga told DW he agreed with the WHO assessment. He noted, however, that the country has learned from past Ebola epidemics.
The outbreak is the ninth in four decades. In Likati, in the northeastern province of Bas-Uele, an outbreak was contained in July, less than two months after it was first reported.
"I think that the experience gained in previous years actually allows us to anticipate. And when such a crisis appears, there are several indicators that we have that allow us to know if it is an epidemic that will only remain in rural areas or if it has the potential to expand in urban areas," Illunga told DW.
"Bikoro is at a road distance close to Mbandaka. So for us, in our plan of response and in all that we had planned, we had put Mbandaka on alert. So, in all our provisions, we had arranged for that," he said.
Vaccine hopeThe international effort to contain the latest outbreak includes a European Union pledge of €1.6 million ($1.9 million) to the WHO and DR Congo.
Newly developed Ebola vaccines are also being used for the second time.
A shipment of 4,000 doses of the vaccine arrived in DR Congo this week. It was developed in the wake of the 2014-16 West African Ebola epidemic that killed more than 11,000 people in Guinea, Liberia and Sierra Leone.
"It's what we call an investigational vaccine, is not yet licensed. It will be implemented within a study protocol which has been accepted by the national authorities and the ethical review board in Kinshasa," Max Gertler of the Institute of Tropical Medicine at Charite Hospital in Germany told DW.
"We have a lot of hope that this may help to counter and contain the outbreak soon," the epidemiologist said. The immediate and strong international response on the ground was a positive move.
"In West Africa, we had several months during which nobody, except the national health systems and MSF (Doctors Without Borders) and some other partners, were responding. That was the main reason for the spread and extent of the outbreak in 2014," he said.
Neighbors on 'high alert'Across Africa, borders and airports have in recent weeks boosted the screening people for signs of the virus. On Friday, DR Congo's neighbors in East Africa became the latest to go on high alert due to the outbreak.
"Five out of six EAC (East African Community) partner states share borders with the DRC and all of them maintain close trade relations with high border traffic," the regional bloc said.
Airports, such as Entebbe in Uganda and Jomo Kenyatta in Kenya, have brought in doctors or special medical equipment to screen passengers.
Congolese refugees were also being screened at the Sweswe Reception Center at Kyaka II Refugee Settlement across the border in Uganda as a precautionary measure, the United Nations said. Tens of thousands of people have fled fighting in Congo in the past year.