Congo's Ebola outbreak has the largest number of confirmed cases within the first month of any episode of the disease, a senior World Health Organization official told a briefing on Tuesday, blaming the surge on its quick spread to urban areas.

The Bundibugyo outbreak in the Democratic Republic of Congo that has infected over 1 000 people and killed 267 was detected late and experts say the virus had already been circulating for months before it was officially declared on May 15. 

WHO's Abdirahman Mahamud told a press briefing in Geneva that part of the reason for the scale of the outbreak was that some early confirmed cases were in urban centres, like Bunia and the mining town of Mongbwalu. Many past outbreaks have first been identified in rural areas and often petered out quickly.

"What is important is we need to scale up and this outbreak is moving faster than us," he told reporters, after returning from Bunia last week. 

He noted signs of hope, highlighting a quick increase in the number of Ebola beds to over 500 in the past fortnight and signs that community resistance and violent resistance to Ebola responders was beginning to abate.

“More and more communities are aware of the risk of Ebola and are asking for tools to support and protect themselves," he said. 

MORE VICTIMS IN OVERCROWDED CAMPS

The two largest previous Ebola outbreaks were one in West Africa, in Guinea, Sierra Leone and Liberia, which killed 11 000 people between 2014 and 2016, and a less fatal outbreak in Congo in 2018.

Ebola cases have now been reported in at least three of eastern Congo's crowded displacement camps.

The International Organization for Migration's Abdoulaye Wone said at the same briefing that at least 25 cases had been confirmed at the camps, including 14 deaths.

"Even in a normal situation before the outbreak, they were facing overcrowding," he said, adding that many leave the camps by day for work or to seek food.

Justin Zanamuzi, director of Catholic aid organization Caritas which is helping at the Kigonze camp, told Reuters that four children there had died since Monday although test results were not yet available.

There have been over 20 outbreaks in sub-Saharan Africa, according to the US Centers for Disease Control and Prevention (CDC).