Concerns about the spread of the disease increased on Thursday when the health agency announced that the first case had been detected in Mbandaka, a city of almost 1.2 million people.
"The confirmed case in Mbandaka, a large urban center located on the main national and international air routes of rivers, roads and nationals increases the risk of spreading within the Democratic Republic of the Congo and towards neighboring countries," said the release.  While the WHO raised the national public health risk to "very high", he said that the overall risk level is "currently low".
The emergency committee of the WHO International Health Regulations will determine on Friday if the current outbreak constitutes a public event health event of international interest.
A total of 45 cases of hemorrhagic fever have been reported now, including 25 deaths, the health ministry said Thursday. Fourteen cases have been confirmed with laboratory tests.
Outbreak enters & # 39; new phase & # 39;
T The case was confirmed in Wangata, one of the three health zones of Mbandaka, the capital of the Equateur province in northwestern Congo. Previously, infections and deaths had been limited to the rural area of Bikoro, almost 150 kilometers away.
The spread of the virus from rural areas to a city has raised fears that it will spread rapidly and become more difficult to control.
"This is a worrying development, but now we have better tools than ever to fight Ebola," said Dr. Tedros Adhanom Ghebreyesus, WHO Director-General. "WHO and our partners are taking decisive action to stop the spread of the virus."
The organization is working with the health NGO Medecins Sans Frontières (MSF) and other partners to increase the number of special isolation rooms to treat patients. It is deploying about 30 experts to conduct surveillance in the city and inform local communities about treatment and prevention methods in collaboration with the country's Ministry of Health.
Hundreds of people infected
The Department of Health first reported the outbreak on May 8, the ninth the country has faced in the last four decades.
"This outbreak is very close to the Republic of the Congo and the Central African Republic, and we take it very seriously," said Dr. Ibrahima-Soce Fall, WHO regional emergency director for Africa, said on Monday. .
Ebola virus disease, which most commonly affects humans and non-human primates, such as monkeys, gorillas and chimpanzees, is caused by one of the five Ebola viruses. On average, about 50% of people who contract Ebola die.
The first human outbreaks of Ebola occurred in 1976, one in the north of what is now Congo and in the region that is now South Sudan.
Humans can be infected by other humans if they come into contact with bodily fluids of an infected person or with contaminated objects of infected people. Humans can also be exposed to the virus, for example, by killing infected animals.
West Africa experienced the largest reported outbreak of Ebola in a two-year period beginning in March 2014; A total of 28,616 confirmed, probable and suspected cases were reported in Guinea, Liberia and Sierra Leone, with 11,310 deaths, according to WHO.
Jennifer Hauser of CNN contributed to this report.