MONROVIA, Liberia -- Liberia released its last Ebola patient, a 58-year old English teacher, from a treatment centre in the capital on Thursday, beginning 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," Beatrice Yardolo told The Associated Press after her release. She kept thanking God and the health workers at the centre.

Yardolo said she had been admitted to the Chinese-run Ebola treatment centre in the Paynesville district of Monrovia on Feb. 18. A mother of five, she is originally from the northeastern county of Nimba near the borders with Guinea and Ivory Coast, but lives in Monrovia where she teaches at a church-run school. The St. Paul's Bridge community where she resides and teaches had become the last "hotspot" for Ebola cases in Monrovia, according to Tolbert Nyenswah, Assistant Health Minister and head of the country's Ebola response.

There are no other confirmed cases of Ebola in the country, and as such Liberia can begin to count up to 42 days to be declared Ebola free in keeping with World Health Organization protocols and standards, Nyenswah said Wednesday. He challenged all Liberians to commit themselves to achieving "zero Ebola infections" by rigidly abiding by the anti-Ebola regulations.

Liberian President Ellen Johnson Sirleaf has said no country can be declared Ebola free until all the other countries have no cases.

Sierra Leone, Liberia and Guinea have been hardest hit in the yearlong Ebola outbreak, which is estimated to have left more than 9,800 people dead.

The WHO on Wednesday reported 132 new Ebola cases last week, an increase from the 99 cases reported the previous week. The agency said the spread of Ebola remains "widespread" in Sierra Leone and noted that cases have jumped both there and in Guinea.

Nine new cases were reported in a 24-hour period, according to an update from the Sierra Leone government on Tuesday.

WHO said only about half of new Ebola patients in Guinea are connected to known cases, meaning that health officials are unable to track where the disease is spreading in the other half of cases.

The UN health agency has said it will start large-scale testing of an experimental Ebola vaccine in Guinea on Saturday to see how effective it might be in preventing future outbreaks of the deadly virus.

The health agency's vaccination strategy in Guinea aims to create a buffer zone around an Ebola case to prevent its further spread. Officials will vaccinate people who have already been exposed to Ebola cases and are at risk of developing the disease.

The vaccine being tested -- VSV-EBOV -- was developed by Canada and is now licensed to Merck. A second vaccine -- one developed by U.S. National Institutes of Health and GlaxoSmithKline -- will be tested in a separate study as supplies become available.

Associated Press Medical Writer Maria Cheng in London contributed to this report.