All three of the West African countries hardest hit by the epidemic — Guinea, Liberia and Sierra Leone — have now documented stopping the original chain of infections that experts believe began in December 2013 with the undiagnosed illness of a young boy, Emile, in the village of Meliandou in Guinea’s forest region.
“This is a very big victory for the nation and the people of Guinea,” said Fode Tass Sylla, a spokesman for the country’s Ebola task force. He thanked other countries, the health organization and private charities for their support.
Two 21-day incubation cycles of the virus have passed since the last person in Guinea with the illness, a 3-week-old girl, twice tested negative for the virus. The country now enters a three-month period of heightened surveillance during which the virus could re-emerge, as it has done twice in neighboring Liberia after that country ended transmission. (In mid-January, human-to-human transmission linked to those cases could be declared ended.)
“We will continue to monitor the situation,” Guinea’s minister of health, Col. Rémy Lamah, a physician, said in a telephone interview. “I congratulate everybody who participated in the fight against Ebola.”
The epidemic killed more than 11,000 people and sickened more than 28,000 across 10 countries, according to estimates released by the World Health Organization. Responders initially failed to recognize the extent and danger of the outbreak, which quickly crossed borders and inspired fear all over the world.
Since then, local, regional and international efforts have been made to end the outbreak.
“It’s important to take a pause and be thankful for where we’ve arrived at and get to work rebuilding that health system and making it more resilient for the future,” said Dr. Rick Brennan, director of Ebola response and coordination at the health organization’s headquarters in Geneva.
The Guinean government announced plans for a celebration with well-known musicians on Wednesday in Conakry, the capital, although some residents said that the country should instead focus on prayer and mourning the dead. Some Guineans expressed hope that the declaration would lead to a resumption of international trade and travel.
“I think now I will get my visa to go to China to buy my goods,” said Dian Diallo, a food importer working in the vast Madina market in Conakry.
“I did not go to hajj this year, and I hope to go to Mecca in 2016 if there is no Ebola,” Mr. Diallo said.
Other Guineans, however, were still focused on what was lost. Camara Fode Abdulai, a fruit seller who survived Ebola, spoke through tears as he described the deaths of 13 members of his family from the disease. He said he worried that other countries would not act quickly enough if another outbreak emerged, adding that customers and even friends still fear coming near him. “Today, I am not doing any business,” he said.
The World Health Organization has documented 10 episodes since March in which a flare-up of Ebola has been linked to the persistence of the virus in certain parts of survivors’ bodies, including the testes. Scientific investigations pointed to sexual transmission in several cases. One baby is thought to have contracted Ebola from the breast milk of a survivor.
Yet in other cases, how the virus re-emerged to cause illness remains a mystery. In November, two brothers and their father contracted the disease in Liberia many weeks after Ebola transmission had ended there. Genetic sequencing showed the virus in the boys to be nearly identical to a strain that had circulated in that country in August 2014, suggesting that it had come from a survivor, according to Dr. Mosoka Fallah, an Ebola response coordinator for the Liberian Ministry of Health.
He added, however, that scientists reported on Monday that they had been unable to derive genetic sequences from samples that might have established a precise link to the new cases.
Dr. Brennan said the World Health Organization was exploring experimental drugs that may help eradicate the last traces of Ebola in people with persistent virus, and experimental vaccines that could help protect their intimate contacts.
Guinea’s last patient, the three-week old girl whose mother died of Ebola, is extremely rare in having survived Ebola at such a young age, Dr. Brennan said. She received two experimental treatments: the antibody combination ZMapp and an antiviral compound made by the pharmaceutical company Gilead.
“She’s doing quite well,” said Dr. Letizia Di Stefano, medical coordinator for Doctors Without Borders in Guinea. The group, which treated Ebola patients throughout the outbreak, has been following up on the baby’s care and plans a celebration to mark the end of Ebola transmission in the country.
“We are quite happy at the moment,” Dr. Di Stefano said. She added that thousands of survivors, many of whom are experiencing health problems, would need continuing medical assistance and psychological support.
Of all the countries where Ebola spread, the virus proved hardest to eradicate from Guinea, experts said. In several cases, Ebola response workers and others who tried to dispel rumors about the illness were attacked, and some were killed.
“There was always an undercurrent of public distrust,” said Dr. Thomas R. Frieden, director of the Centers for Disease Control and Prevention in Atlanta. He traveled to Guinea four times during the outbreak and sent teams of experts to work there alongside colleagues from Canada and the Democratic Republic of Congo.
Unlike in Liberia and Sierra Leone, where treatment centers in major cities were overwhelmed and dramatic scenes of suffering on the streets inspired public mobilization, in Guinea the epidemic simmered at a relatively low level for many months. Consequently, when Ebola reached new areas in the large country, communities did not fully appreciate its seriousness.
“In a way, their lack of explosive spread worked against them,” Dr. Frieden said.