After seeing people fall to the deadly virus in area after area, Liberia said two people had succumbed to the virus in Sinoe province, the last Ebola-free bastion in a country that has seen the biggest toll with 624 deaths.
The virus has spread relentlessly through Liberia, Guinea and Sierra Leone, and Nigeria has also been affected despite showing some progress in fighting the epidemic, which has killed 1,427 people since March.
"(Sinoe) was the last area untouched by Ebola," George Williams, head of the Health Workers Association of Liberia, told AFP.
The country has witnessed chaotic scenes in recent days following a surge in the number of patients dying of the hemorrhagic fever.
Aid workers said crematoriums in the capital of Monrovia were struggling to deal with bodies arriving every day, and earlier this week, violence erupted in an Ebola quarantine zone in the capital after soldiers opened fire on protesting crowds.
In a bid to ease the crisis, medical charity Doctors Without Borders (MSF) is working on nearly quadrupling the capacity of its Ebola centre in Monrovia.
"Currently we have around 60 patients for a capacity of 120 beds," said Henry Gray, an MSF coordinator.
"And we are making our site bigger. In the next 10 days, we hope to have a location that can welcome up to 400 patients."
In neighbouring Nigeria, officials said Friday that two more people had tested positive for Ebola, taking the total number of confirmed cases to 14, including five deaths.
In a news conference in Monrovia, WHO Assistant Director-General Dr Keiji Fukuda on Friday warned efforts to combat the disease would take some time.
"This is not something to turn around overnight, it is not going to be easy; we expect several months of hard work. We expect several months really struggling with this outbreak," he said at a press conference alongside Dr David Nabarro.
Nabarro, a physician appointed by the United Nations last week to coordinate the global response to the worst-ever outbreak of the disease, was in Monrovia as part of a tour of the region.
Speaking to AFP, he said he was determined to "ensure that every piece of our apparatus is at its optimum so it could deal possibly with a flare-up if that's necessary".
Nabarro is also due to visit Freetown, Conakry and Abuja during the trip, where he is tasked with revitalising the health sectors of affected countries.
No cure or vaccine is currently available for the deadly virus, which is spread by close contact with body fluids, meaning patients must be isolated.
However, two American missionaries who contracted Ebola while treating patients in Liberia made a full recovery in the United States. The two were treated with experimental drugs.