The Ebola outbreak that began in the Democratic Republic of Congo in April was declared officially over on Tuesday in what appeared to be twin triumphs for a new vaccine and rapid response.
Just 33 people died, even though the outbreak reached Mbandaka, a river port city of over one million people. At one point, experts had feared the virus might spread throughout Central Africa.
Three years ago, an Ebola outbreak in West Africa cost more than 11,000 lives. Health agencies were slow to respond, and no vaccine was available until it was nearly over.
The last known case in Congo occurred in early June, and the World Health Organization declared the outbreak “largely contained” three weeks later. Declaring it officially over, however, required waiting 42 days — the length of two viral incubation periods.
Tedros Adhanom Ghebreyesus, the W.H.O.’s director-general, joined Dr. Oly Ilunga, Congo’s health minister, in making the announcement in the capital, Kinshasa. Dr. Tedros thanked “the tireless efforts of local teams, the support of partners, the generosity of donors and the effective leadership of the Ministry of Health” in Congo.
The W.H.O., which was harshly criticized for failing to react in 2015, moved quickly in early May as soon as a handful of hemorrhagic fever deaths in Congo were confirmed to have been caused by Ebola.
The organization released $2 million from its emergency fund and sent its first support team from Geneva.
As of Tuesday, the agency had asked donors for $57 million to fight the outbreak, and donations to all entities involved in containing the outbreak amounted to $63 million, according to the United Nations Office for the Coordination of Humanitarian Affairs.
By contrast, stopping the 2014-2015 outbreak in West Africa cost donors more than $3.6 billion, according to the Centers for Disease Control and Prevention. In addition, the World Bank calculated that the three countries involved — Guinea, Sierra Leone and Liberia — lost a total of more than $2.2 billion in gross domestic product.
Even though Congo is familiar with Ebola — this was the country’s ninth outbreak since the disease first appeared in 1976 — more than 350 support personnel were deployed there. They included vaccinators from Guinea, where a novel Ebola vaccine was first field-tested.
The Congo outbreak marked the first in which an Ebola vaccine was readily available. In addition to giving injections to all front-line health care workers, experts used “ring vaccination” to protect all contacts of each person with the disease. More than 3,300 people were vaccinated.
The vaccine, made by Merck and known as rVSV-ZEBOV, must be kept at 80 degrees below 0 Celsius (-112 degrees Fahrenheit), so advanced freezers and storage containers had to be deployed to Mbandaka and to Bikoro, a market town closer to the outbreak’s epicenter.
The outbreak began in villages in the Ikoko-Impenge area, some of which were reachable only by motorbike or foot.
Four experimental treatments consisting of antiviral drugs or cloned antibodies were also made available, but the outbreak was contained before they could be used.
The rapid success against Ebola “should make the government and partners confident that other major outbreaks affecting the country, such as cholera and polio, can also be tackled,” Dr. Tedros said.