A Red Cross burial team wore protective equipment in 2014. (Pete Muller/Prime for The Washington Post)

About a year and a half after it emerged, the Ebola outbreak in Sierra Leone has officially ended.

Nearly 4,000 Sierra Leoneans — among more than 11,000 West Africans — died of the disease. It came upon some slums and villages like a wave, infecting scores overnight and posing one of the most significant public health challenges in recent history.

Global health officials and members of the country’s government gathered Saturday in the capital to mark the milestone. The World Health Organization said 42 days had passed since the last recorded case, the agency’s criteria for declaring the end of an outbreak.

“It’s been a very, very long journey,” said Anders Nordström, WHO’s representative in Sierra Leone. “People are both relieved, tired and sad. There’s a feeling of ‘Yes, we did it.’ But also recognition of the many people who suffered.”

The outbreak began in December 2013 in Guinea, where efforts continue to eradicate the disease, but quickly crossed into Sierra Leone and Liberia, all among the world’s poorest countries, with limited medical systems. International health organizations were slow to respond, mobilizing only after the disease had spread across vast stretches of West Africa.

Although Liberia was declared Ebola-free in September, neighboring Guinea is still trying to stamp out the virus. WHO recorded seven new cases of the disease in Guinea in the past three weeks.

Sierra Leone had only 120 doctors before the epidemic, and at least 11 of them died of the disease. Now, the country will have to rebuild its health-care system as it reels from the economic blow delivered by the virus. Even before the disease struck, Sierra Leone had one of the world’s highest maternal and child mortality rates. International aid organizations have pledged to help the country recover.

Before Ebola arrived, Sierra Leone’s economy was expected to grow by about 11 percent in 2014 — making the country one of West Africa’s economic bright spots. The World Bank now estimates that Sierra Leone’s economy will shrink by 23.5 percent this year and will lose $1.4 billion in growth as a result of the outbreak.

In trying to stem the spread of the virus, officials experimented with quarantines and tracing the contacts of victims. Those practices initially angered rural communities, where residents saw the disease as a kind of curse that tore families apart. As public cemeteries overflowed, many victims went into hiding, causing the virus to expand even further. The government response was widely criticized as ineffective.

“When Ebola proved real enough, political machinations and manipulation needlessly hindered the early response,” said a report released in late October by the International Crisis Group, a research organization.

It took roughly a year before public health officials saw the impact of their work and the transmission numbers began to decline. Even then, cases continued to emerge in far-flung parts of the country.

Many treatment centers and labs have already been removed, but others will remain in case the virus has a resurgence. They may also be used to treat other illnesses.

“We still have to be watchful at all time,” said Ishmael Foday, the paramount chief of Kalahoun district, where the disease first emerged in Sierra Leone. “This can be reversed. The way Ebola comes is forgetfulness.”

Foday, who lost his son to the disease, now walks through the district, scanning the rooms where victims once lived.

“We look at the empty houses where entire families died. They serve as constant reminders to us,” he said.

Corrrection: An earlier version of this article incorrectly said that more than 11,000 Sierra  Leoneans died of the disease and at least 17,000 survived it. This version has been updated to reflect the accurate figures.

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