Ebola, a haemorrhagic fever, killed at least 11,000 across the world after it decimated West Africa and spread rapidly over the space of two years.
That pandemic was officially declared over back in January 2016, when Liberia was announced to be Ebola-free by the WHO.
The country, rocked by back-to-back civil wars that ended in 2003, was hit the hardest by the fever, with 40 per cent of the deaths having occurred there.
Sierra Leone reported the highest number of Ebola cases, with nearly of all those infected having been residents of the nation.
WHERE DID IT BEGIN?
An analysis, published in the New England Journal of Medicine, found the outbreak began in Guinea – which neighbours Liberia and Sierra Leone.
A team of international researchers were able to trace the pandemic back to a two-year-old boy in Meliandou – about 400 miles (650km) from the capital, Conakry.
Emile Ouamouno, known more commonly as Patient Zero, may have contracted the deadly virus by playing with bats in a hollow tree, a study suggested.
An infected child is led away by a nurse at the Medecins Sans Frontiers centre in Monrovia, Liberia in 2014
Figures show nearly 29,000 people were infected from Ebola – meaning the virus killed around 40 per cent of those it struck.
Cases and deaths were also reported in Nigeria, Mali and the US – but on a much smaller scale, with 15 fatalities between the three nations.
Health officials in Guinea reported a mysterious bug in the south-eastern regions of the country before the WHO confirmed it was Ebola.
Ebola was first identified by scientists in 1976, but the most recent outbreak dwarfed all other ones recorded in history, figures show.
HOW DID HUMANS CONTRACT THE VIRUS?
Scientists believe Ebola is most often passed to humans by fruit bats, but antelope, porcupines, gorillas and chimpanzees could also be to blame.
It can be transmitted between humans through blood, secretions and other bodily fluids of people – and surfaces – that have been infected.
IS THERE A TREATMENT?
The WHO warns that there is ‘no proven treatment’ for Ebola – but dozens of drugs and jabs are being tested in case of a similarly devastating outbreak.
Hope exists though, after an experimental vaccine, called rVSV-ZEBOV, protected nearly 6,000 people. The results were published in The Lancet journal.