After a rapid response by health agencies and the rollout of a new vaccine, an Ebola outbreak in the Democratic Republic of Congo has been declared “largely contained” by the World Health Organization.
The outbreak was the first in which health authorities deployed a Merck vaccine field-tested in the waning days of the huge 2014 epidemic in West Africa.
More than 3,200 people were vaccinated in Congo; they included front-line health care workers, as well as family members and friends who had been in contact with known Ebola victims.
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None of those vaccinated became ill, the Congolese health ministry said.
As of Tuesday, 53 cases that were laboratory-confirmed or considered “probable” had been detected, and 29 patients had died, according to the ministry. Although suspected cases continue to be reported, none have been confirmed by a laboratory since June 6.
As of Wednesday more than 1,500 contacts of the confirmed or probable cases had been followed for 21 days and had not displayed Ebola symptoms, the W.H.O. said. Three weeks is considered the maximum incubation period for the infection.
Nonetheless, the outbreak will not officially be declared over until at least one more 21-day incubation period has passed, and the Congolese health ministry will continue surveillance after that.
Some men who recover from Ebola retain virus in their semen for weeks and can pass it on through sex, although that has never triggered a large outbreak.
The outbreak appears to have begun with a cluster of 21 cases of illness and 17 deaths in April in the remote Ikoko-Impenge rural area. It was officially declared an Ebola outbreak on May 8, when lab testing done in Kinshasa, Congo’s capital, confirmed that two patient samples had the virus.
This was the ninth Ebola outbreak in Congo since the disease was first discovered in 1976, but it was brought under control in seven weeks even though cases quickly reached a major city — Mbandaka, a river port with over 1 million people.
Only four cases were found in Mbandaka, and the vaccine was rolled out there almost immediately. It took much longer to get the vaccine to scattered villages that could be reached only by motorcycle.
The W.H.O. deployed 258 experts to fight the outbreak. Three mobile laboratories and four treatment centers were set up; three centers were run by Doctors Without Borders, and the fourth by the medical charity Alima, the Alliance for International Medical Action.
Four experimental treatments for Ebola were sent to the region: ZMapp, which was tried in West Africa; GS-5734, an antiviral drug; and two monoclonal antibodies, REGN-EB3 and Ma b114. But the outbreak waned before definitive clinical trials could be run.
Sixty children were orphaned in Congo. Twenty-four people were cured, and a follow-up clinic for them was established.
Donors provided four ambulances, numerous motorcycles and megaphones, and thousands of bleach tablets. Dozens of educational talks explaining the disease were organized.
About 115 routes by which residents might leave the area and spread the virus were mapped, but intensive surveillance looking for feverish or obviously ill persons could be set up at only 30 of them, the W.H.O. said.
Donors gave $34 million toward stopping the outbreak. The W.H.O. initially spent $4 million from its emergency fund and asked for $26 million; as the outbreak expanded, the organization sought $57 million.