Aiming to squelch an Ebola outbreak that has infected 54 people, killing almost half of them, aid workers in the Democratic Republic of the Congo have begun giving an experimental vaccine to people in the rural region at the epicenter of the outbreak.
Epidemiologists working in the remote forests have not yet identified the first case, nor many of the villagers who may have been exposed. Investigators will need to overcome extreme logistical hurdles to reconstruct how the virus was transmitted, vaccinate contacts and halt the spread.
“For an epidemic to be under control, you need a clear epidemiological picture,” said Dr. Henry Gray, the emergency coordinator for Doctors Without Borders.
“If you don’t know the stories of the people involved — who their families were, what their jobs were, where they went to weddings and funerals — then you don’t know the epidemic.”
Almost 500 people received the experimental vaccine, VSV-EBOV, last week around Mbandaka, a riverfront city of more than 1.5 million people where four Ebola cases have been confirmed.
Mbandaka is a priority because it is a traffic hub. The Republic of the Congo lies just across the Congo River, and Kinshasa, Congo’s capital of 10 million, is less than 500 miles downstream.
Aid workers are using the ring method: The vaccine is given to groups of people in contact with each Ebola case, such as family caregivers, as well as the contacts of those contacts.
About 7,500 doses are available to vaccinate 50 rings of 150 people each, according to Dr. Peter Salama, the deputy director-general for emergency response at the World Health Organization. An additional 8,000 doses will follow.
The W.H.O. is monitoring more than 900 contacts throughout Équateur province. As the vaccination program expands to the Bikoro and Iboko communities, where most cases have been reported, teams are relying on contact tracing to identify the most urgent recipients.
“This is where everything gets more complicated,” said Chiran Livera, the operation leader in Congo for the International Federation of Red Cross and Red Crescent Societies.
The villages surrounding Bikoro and Iboko are among the most isolated and densely wooded pockets of Congo. Aid workers must use motorbikes to navigate cratered dirt roads that flood during the rainy season. Maps of some regions are incomplete, and vast gaps in cellular service thwart efforts to report data to central operations.
“Following the virus’s narrative may sounds easy to do on a suburban street outside Chicago,” said Dr. Salama. “But when you’re traveling hundreds of kilometers in a forest by motorbike to find each person, that’s very different epidemiological work.”
If the outbreak worsens, a second vaccination may be offered to health workers. That vaccine, developed by Johnson and Johnson, requires two doses and would take longer than VSV-EBOV’s seven to 10 days to become effective — but may protect health workers for several years.
The Congolese Ministry of Health is planning to deploy up to five experimental treatments, though the two most highly recommended by the W.H.O. may prove impractical in a remote setting.
ZMapp, a cocktail of three antibodies used in West Africa, must be given in multiple doses and must be refrigerated. Remdesivir, a drug developed by Gilead Sciences, requires intensive monitoring of liver and kidney function — nearly impossible for treatment centers without electricity, running water or standard equipment.
Another option, called MAb114, began safety trials earlier this month. Made from the antibodies of an Ebola survivor, it can be crystallized and reconstituted with saline-like fluids in the field.
“These are all investigative products,” Dr. Salama said. Vaccine makers have struggled to show efficacy without live Ebola cases in which to test their drugs. “Many consider this outbreak their chance to prove themselves,” he said.
Drug companies are not alone in that mission.
The W.H.O.’s emergency committee gathered 10 days after the Congolese government notified the organization of an Ebola case, a stark contrast to the West African epidemic in 2014, when the group did not convene until almost 1,000 people had died.
Since May 8, the W.H.O. has sent 156 technical experts to the region. A mobile laboratory has been set up to expedite case confirmations in Bikoro; another is planned for Mbandaka. A cellular tower has been erected in Mbandaka to help workers trace people who may have been infected throughout the region.
The W.H.O. has more than doubled its budget request to $56 million from $26 million to account for the possibility of the virus may reach an urban setting.
“The biggest problem of 2014 was that there had never been an Ebola epidemic before,” said Ron Klain, the White House’s Ebola response coordinator for West Africa. “This time, there is an intensity, a focus, a pace. No one is underestimating the risk, and that alone is a big advantage.”
Another advantage is context: Unlike West Africa, Congo has experienced eight previous Ebola outbreaks since the virus was identified in 1976. Aid workers who arrived in Kinshasa this month found pre-established surveillance protocols, according to Mr. Livera.
The W.H.O.’s strategy assumes the virus will ultimately infect 100 to 300 people. Each rural case may infect 10 contacts, and each urban case may infect 30. Response activities may continue into July, according to a revised plan released May 27.
Until investigators identify the index case, it is impossible to discern whether the first patient detected in April was truly the first human case or the hundredth, according to Dr. Gianfranco Rotigliano, the regional director of Unicef. Until then, it is impossible to quantify the crisis.
“These are the early days of the outbreak,” Dr. Salama said. “There can be lulls. We’ve seen that before. But there only needs to be one event — a super-spreader, like a funeral — to cause an explosion.”