The three countries hit hardest by the Ebola epidemic have recorded their lowest weekly number of new cases for months, according to the World Health Organisation.
As the global death toll reached 8,429 out of 21,296 cases reported so far, Sierra Leone and Guinea both saw the lowest weekly total of confirmed Ebola cases since August 2014.
Liberia, which reported two days with zero new cases last week, had its lowest weekly total since June, WHO said on Wednesday.
UN Secretary-General Ban Ki-moon previously said the epidemic could be over by mid-2015 but WHO is now declining to set a specific timeline after having been proved wrong on previous predictions.
"WHO hopes Ebola ends as soon as possible in all three affected countries of Sierra Leone, Liberia and Guinea," Winnie Romeril, WHO spokeswoman, told Associated Press news agency.
"WHO is not predicting how soon Ebola will end as it would take every community to use the facilities and resources available to them."
She said getting to zero cases will take time and effort that includes immediate treatment of patients and dignified, safe burials of the dead.
Sierra Leone's President Ernest Bai Koroma predicted this week that his country would be Ebola-free by WHO standards by May.
By WHO standards, a country cannot be declared Ebola-free until it has registered no cases for 42 consecutive days.