The outbreak - the 17th in the DR Congo and the third-largest since Ebola was discovered half a century ago - is outpacing the global response, something WHO director-general Tedros Adhanom Ghebreyesus acknowledged this week before travelling to Kinshasa on Thursday.
His visit came as Brazil said on Saturday it was investigating a suspected Ebola case in Sao Paulo state involving a man who recently visited DR Congo.
Authorities said the patient was in isolation at a specialist hospital.
After meeting Prime Minister Judith Suminwa Tuluka on Friday, Tedros flew on Saturday to Bunia, capital of Ituri province, where the first cases were confirmed earlier this month.
At a press conference alongside DR Congo's health minister, Tedros said the rare Bundibugyo strain has no approved vaccines or treatments, making early palliative care - including isolation, rehydration and pain management - critical.
"Seeking care early makes a real difference," he said.
He also urged residents to practice safe burials, warning the bodies of Ebola victims are highly contagious.
"I understand how painful it is to lose someone and how much it means to honour them properly," he said.
"While we grieve for those we have lost, we must do everything we can so that we do not lose another."
There have already been multiple attacks on health facilities by crowds seeking to reclaim bodies for traditional burials, in which family members handle the body without proper protective equipment.
The WHO said on Friday there were 906 suspected cases of Ebola in DR Congo, including 223 suspected deaths under investigation.
Health Minister Samuel Roger Kamba said later on Friday authorities had identified 1028 suspected cases, with 225 confirmed.
Health officials and aid workers say they lack even basic supplies such as masks after the outbreak spread undetected for weeks.
Medical charity Medecins Sans Frontieres warned on Saturday the response was inadequate.
"Never before has an Ebola outbreak recorded so many cases so soon after its declaration," Dr Alan Gonzalez, MSF deputy director of operations, said in a statement.
"Like everyone in the affected areas, MSF teams are witnessing a response that has not yet caught up to the rapid spread of the epidemic."
The number of medical organisations on the ground and the level of support remain far short of what is needed, Gonzalez added.
On arriving in Kinshasa on Thursday, Tedros called for more international support, saying the WHO had received only about a third of the funding it requires.
Ebola cases have been confirmed in three of DR Congo's provinces and in neighbouring Uganda, which this week closed its border with DR Congo.
Kamba has spent several days in Ituri ahead of Tedros's visit.
At a press conference on Thursday, he rejected reports suggesting the outbreak was "out of control".
On Saturday, appearing alongside Tedros, he said health officials had sufficient resources to meet testing needs, even as MSF said "hundreds of samples remain untested".
DR Congo's experience with Ebola, including a small outbreak last year, would help contain the disease, Kamba said, adding neighbouring countries should keep borders open.
"We have experience with epidemics. We defeated Ebola last year. We tell you, trust us, we know what we are doing."
with DPA
