World Health Organization to declare Ebola outbreak over

The WHO said Thursday's announcement in Geneva will “mark 42 days since the last Ebola cases in Liberia were tested negative.”

“We will remain careful and keep calling on the population to take the necessary measures in preventing reoccurrence,” said Francis Karteh, Liberia's chief medical officer and a major figure in the response to the epidemic.

Liberia, the hardest hit country in the outbreak with 4,800 deaths, discharged its last two cases — the father and younger brother of a 15-year-old victim — on Dec. 3.

It was the last country affected by an outbreak infecting almost 29,000 people and claiming 11,315 lives, according to official data, which most experts believe is an underestimate.

The patients' recovery triggered a 42-day countdown — twice the incubation period of the virus — before Liberia can be declared free of transmission for a third time.

Ebola can fell its victims within days, causing severe fever and muscle pain, weakness, vomiting and diarrhea. In many cases it shuts down organs and causes unstoppable bleeding. The virus is spread through close contact with the sweat, vomit, blood or other bodily fluids of an infected person, or the recently deceased.

Liberia was first declared free of human-to-human transmission in May, only to see the fever resurface six weeks later. It was officially credited with beating the epidemic for a second time in September before another small cluster of cases emerged.

The virus spread aggressively from “patient zero,” a Guinean infant who became the first victim, into Liberia and then Sierra Leone.

Sporadic cases were also registered in Mali, Nigeria and Senegal as deaths mounted at a dizzying rate, igniting fears in Europe and elsewhere of a virus that transgressed borders and national controls.

The epidemic devastated the economies of the worst-hit countries, as crops rotted in the fields, mines were abandoned and goods could not get to market.

Strong recent growth has been curtailed in Guinea and while Liberia has resumed growth, Sierra Leone is in a severe recession according to the World Bank, which has mobilized $1.62 billion for Ebola response and recovery efforts.

During the two months of peak transmission in August and September 2014, Liberia's capital Monrovia was the setting for some of the most harrowing scenes from the outbreak.

The largest Ebola unit ever built opened there with 120 beds in August 2014 but was immediately overwhelmed, with staff forced to turn patients away at its gates, despite more than doubling its capacity.

Liberian Defense Minister Brownie Samukai told a meeting of the U.N. Security Council that the country was facing “a serious threat to its national existence.”

At the time, more than 400 new cases were being reported each week, with uncollected and highly infectious bodies piling up in the streets of Monrovia, a sprawling, chaotic city at the best of times.

The international community came under fire for a response that experts felt was belated and insufficient.

But while criticized initially for indifference, the West later rallied to the cause, sending thousands of troops and medics to Africa in 2014 and developing possible treatments and vaccines, many of which are still being tested.

Al Jazeera and Agence France-Presse