Ebola, a hemorrhagic fever, killed at least 11,000 worldwide after it decimated West Africa and expanded rapidly within two years.
That pandemic was officially declared in January 2016, when Liberia was announced as free of Ebola by WHO.
The country, shaken by consecutive civil wars that ended in 2003, was the most affected by the fever, with 40 percent of the deaths occurring there.
Sierra Leone reported the largest number of cases of Ebola, and almost all those infected were residents of the nation.
WHERE DID IT BEGIN?
An analysis, published in the New England Journal of Medicine, found that the outbreak began in Guinea, which is near Liberia and Sierra Leone.
A team of international researchers managed to track the pandemic until it reached a two-year-old boy in Meliandou, about 400 miles (650 km) from the capital, Conakry.
Emile Ouamouno, better known as Patient Zero, may have contracted the deadly virus by playing with bats in a hollow tree, a study suggested.
An infected child is taken by a nurse in the center of Medecins Sans Frontiers in Monrovia, Liberia in 2014
The figures show that almost 29,000 people were infected with Ebola, which means that the virus killed around 40 percent of those affected.
Cases and deaths were also reported in Nigeria, Mali and the United States, but on a much smaller scale, with 15 deaths among the three nations.
Health officials in Guinea reported a mysterious error in the southeastern regions of the country before the WHO confirmed that it was Ebola.
Ebola was first identified by scientists in 1976, but the most recent outbreak eclipsed all others recorded in history, according to the figures.
HOW HUMANS COULD HAVE THE VIRUS?
Scientists believe that Ebola is most often transmitted to humans by frugivorous bats, but you can also blame antelopes, porcupines, gorillas and chimpanzees.
It can be transmitted between humans through the blood, secretions and other bodily fluids of people and surfaces that have become infected.
IS THERE A TREATMENT?
The WHO warns that "there is no proven treatment" for Ebola, but dozens of drugs and punctures are being tested in the case of a similarly devastating outbreak.
However, there is hope, after an experimental vaccine, called rVSV-ZEBOV, which protected almost 6,000 people. The results were published in The Lancet magazine.