The Democratic Republic of Congo faces a "very high" public hazard from Ebola after the malady was affirmed in one patient in a big city, the World Health Organization said on Friday, raising its appraisal from "high" beforehand.

The risk to countries in the region was now "high", raised from "moderate", but the global risk remained "low".

The reassessment came after the case in Mbandaka, a city of around 1.5 million. Past reports of the sickness had all been in remote zones where Ebola may spread all the more gradually.

"The confirmed case in Mbandaka, a large urban centre located on major national and international river, road and domestic air routes increases the risk of spread within the Democratic Republic of the Congo and to neighbouring countries," the WHO said.

WHO statement said there had been 21 suspected, 20 probable and 3 confirmed cases of Ebola between April 4 and May 15 (Reuters)

WHO Deputy Director-General for Emergency Preparedness and Response Peter Salama had told reporters on Thursday that the risk assessment was being reviewed.

"We're certainly not trying to cause any panic in the national or international community," he said.

"What we're saying though is that urban Ebola is a very different phenomenon to rural Ebola because we know that people in urban areas can have far more contacts so that means that urban Ebola can result in an exponential increase in cases in a way that rural Ebola struggles to do."

Later on Friday, the WHO will convene an Emergency Committee of experts to advise on the international response to the outbreak, and decide whether it constitutes a "public health emergency of international concern".

The bad dream situation is a flare-up in Kinshasa, a swarmed city where millions live in unsanitary ghettos not associated with the sewer framework. 

The WHO articulation said there had been 21 suspected, 20 likely and 3 affirmed instances of Ebola between April 4 and May 15, an aggregate of 44 cases, including 15 passings. 

Mbandaka had three presumed cases notwithstanding the affirmed case. 

The WHO is sending 7,540 measurements of an exploratory immunization to attempt to stop the flare-up in its tracks, and 4,300 dosages have just landed in Kinshasa. It will be utilized to ensure wellbeing specialists and "rings" of contacts around each case. 

The antibody supplies will be sufficient to immunize 50 rings of 150 individuals, the WHO said. 

Starting at 15 May, 527 contacts had been distinguished and were being followed up and observed, it said.