Liberia has released its last Ebola patient and begun its countdown to being declared Ebola free.

"I am one of the happiest human beings today on earth because it was not easy going through this situation and coming out alive," 58-year old English teacher Beatrice Yardolo told the AP news agency after her release.

She kept thanking God and the health workers at the Chinese-run Ebola treatment centre in the Paynesville district of Monrovia, where she was admitted to the on February 18.

Her release came as the World Health Organisation (WHO) announced that Liberia had gone a week without reporting any new cases of Ebola - for the first time since last May.

Liberia "reported no new confirmed cases" during the week to March 1, the UN health agency said in a report late on Wednesday.

Since the outbreak began in December 2013, 23,969 people in nine countries have been infected with the virus, and 9,807 of them have died, according to the latest figures.

Of those, 9,249 cases, including 4,117 deaths, were in Liberia, which six months ago was reporting more than 300 new cases each week.

At the height of the epidemic in a country whose health infrastructure had been ravaged by two back-to-back civil wars, overflowing health clinics had to turn away people, often to die on the streets.

But a huge national and international response helped stem the spread.

Of 45 samples tested nationwide last week, none were positive, WHO said, adding that it was first time there had been no new confirmed cases since May 26, 2014.

The outlook was less positive in Guinea and Sierra Leone, the other countries affected by the outbreak, which jointly reported 132 new confirmed cases last week.