WHO Director-General Tedros Adhanom Ghebreyesus arrived in Kinshasa, the Democratic Republic of the Congo's capital, late on Tuesday night and is scheduled to meet partners and Congo's president, Felix Tshisekedi.
It's his second visit to the country since the outbreak was declared in mid-May.
The Ebola outbreak reached 3874 cases, including 1751 deaths as of Monday, according to the latest data published overnight by Congo's health ministry.
The outbreak has eclipsed all other Ebola outbreaks in history in terms of rate of transmission and is the second-largest outbreak on record, only behind the 2014-2016 West Africa outbreak that recorded more than 28,000 cases, including over 11,000 deaths.
The Bundibugyo virus that is causing the outbreak has no approved treatment or vaccine, and local officials believe the outbreak had been raging on in a remote part of eastern Congo long before it was declared on May 15.
Most of the new cases being recorded in the outbreak are outside of contacts being monitored after their exposure to patients, showing that Ebola is still spreading faster than the response that has been expanding.
In Ituri province, the epicentre which accounts for nearly 90 per cent of cases, many localities are still not accessible due to safety concerns amid rebel conflict.
Many health workers have gone on strike to protest lack of payment, although some have reported receiving their payment in recent days.
The Africa Centers for Disease and Control director-general Jean Kaseya said on Tuesday when he visited Bunia, Ituri's capital, that contact tracing was mpt working, with at least 60-70 per cent of new cases coming outside of the contact list.
"We need to be innovative on the way to approach the contact list," Kaseya said.
Late detection of cases remains challenging and has been a key contributing factor to the 45 per cent fatality rate, officials say.
The 77 new cases reported in the previous 24 hours included 44 deaths, according to the health ministry's update.
At least 717 patients are in isolation while 749 patients have recovered.
