The CDC is stepping up efforts to fight an Ebola outbreak that is threatening to spread beyond the borders of the Democratic Republic of Congo (DRC).

The World Health Organization (WHO) recently declared an international health emergency in DRC after an Ebola case appeared July 14 in Goma, a city of 2 million people that has connecting flights to global air travel. As of Aug. 2, there have been four cases in Goma, WHO reports.1

“Right now, we have about 15 people on the ground in the DRC and in Goma responding to the outbreak,” said Henry Walke, MD, MPH, director of the Division of Preparedness and Emerging Infections at the CDC. “We plan on doubling that number of responders in the next month and maintaining a presence in Goma, [DRC capital] Kinshasa, and perhaps in other large urban areas to prepare for the spread of the outbreak.”

As of July 31, 2019, there have been 2,713 Ebola cases in DRC, including 148 healthcare workers. Overall, 1,813 people have died of Ebola during an outbreak that started in the DRC on Aug. 1, 2018. On July 8, 2019, WHO declared a Public Health Emergency of International Concern.2

The CDC activated its emergency response in June, allowing the agency to provide more resources and fast-track its response. As of July 31, more than 200 CDC personnel have been deployed in the area, Walke said at a CDC press conference.

“There are no cases of Ebola in the United States,” he emphasized. “At this time, we believe the risk to the U.S. from the current Ebola outbreak in DRC remains low, based on the travel volume.”

There are no direct flights between DRC and the United States, and fewer than 16,000 people a year travel to the United States from DRC, he said.

“However, risk of spread from DRC into neighboring countries is high,” Walke said. “The CDC is coordinating with health officials in DRC, Uganda, Rwanda, and South Sudan.”

Civil unrest and armed conflict in DRC have made it difficult to contain the outbreak, which is spreading despite an apparently effective experimental Ebola vaccine.

“Ongoing violence, community distrust, and other unprecedented problems have complicated the public health response,” Walke said.

The Ebola response also has been undermined by people wary of both the vaccine and the intensive questioning and follow-up after detection of a case.

“In terms of trust from the community, it is not only related to vaccine,” he said. “It is also related to basic public health measures, which include case identification, early isolation, and then monitoring the contacts of that case.”

In the classic “ring” method used against smallpox, the idea is to vaccinate contacts of cases and go out another layer and vaccinate the contacts of those contacts.

“As we try to implement contact tracing and identify people who need vaccination, it’s a very mobile population,” he said.

International Emergency

In declaring an international emergency, WHO is calling for international aid and assistance while emphasizing that it would be counterproductive to shut down travel to the region.

“One of the reasons they held off in making the emergency declaration, even though many people felt the conditions had been met previously, was out of fear that countries would implement travel and trade restrictions,” says Jennifer B. Nuzzo, DrPH, SM, a senior scholar at the Johns Hopkins Center for Health Security. “Everybody thinks that is a bad idea,” she tells Hospital Infection Control & Prevention. “That is not the way you try to control the spread of Ebola. It can really slow down the response because aid workers, supplies, and other resources can’t get into the region where they are needed.”

The Ebola outbreak primarily has infected people in the DRC provinces of North Kivu and Ituri.

The four cases in Goma, including two deaths, have raised fears of Ebola spreading to other regions on the continent. It also could open a path out of Africa for the deadly virus. Although there are no direct flights to the U.S., Goma flights to Ethiopia, for example, can connect for travel to the U.S., Europe, and Asia. The incubation period for Ebola is two to 21 days, with most cases showing symptoms at eight to 10 days.

As confirmed on July 14, the first case in Goma traveled there by bus and visited a local clinic for illness. He died the same day while transferring to an Ebola treatment center. Two weeks later, an unrelated case in Goma was identified, a miner who subsequently infected his child and spouse, WHO reported.

“Other suspected cases among contacts are awaiting test results,” WHO said.

While the outbreak response in DRC has been undermined by civil unrest and violence, Goma has a public health presence that already included advisors from the CDC, Nuzzo says.

“[The CDC] was able to participate in the Goma investigation, and they found that some of the PPE that was used in evaluating the [first] patient had been taken home [by caregivers],” she says. “Those are the kind of problems that may go unnoticed unless you have a very keen eye on what is going on. That is enormously helpful. If there is any good news, I think it is the occurrence of cases closer to where the CDC personnel are located.”

Healthcare Worker Deaths

Of the 148 healthcare workers infected, unverified reports indicate at least 40 have died of Ebola. In addition, marauding militia groups vying for control of the region have attacked healthcare workers in some 200 incidents, resulting in seven deaths and 58 wounded.3 No infections or deaths have been reported in deployed CDC personnel.

As previously reported, healthcare workers in DRC are receiving the experimental Ebola vaccine, but the efficacy of immunization was not clear as this report was filed. The WHO reported one incident in which two healthcare workers were infected with Ebola despite receiving the vaccine. The vaccine has demonstrated high efficacy in one clinical trial,4 but is used now on an unprecedented scale.

“Studies so far have suggested a very high rate of vaccine effectiveness, but you can envision there are some people who won’t have a protective response as the numbers get larger,” Nuzzo says. “In many of these cases, it is more likely they were vaccinated too close to when the exposure occurred. They weren’t able to mount a full protective response. Sometimes, they have been vaccinated after an exposure.”

The vaccine appears to be effective against mortality, but it is difficult to determine the efficacy with any precision during an ongoing outbreak, Anthony Fauci, MD, director of the NIH National Institute of Allergy and Infectious Diseases, said at the CDC press conference.

“Certainly, there have been infections among individuals who have been vaccinated,” Fauci said. “The potential benefit of the vaccine is that in those who were vaccinated and did get infected, the mortality rate is extremely low. In fact, I don’t think any of them who have died were vaccinated.”

There have been reports of nosocomial transmission within healthcare settings and treatment centers, but the proportion of these cases within the overall outbreak is unclear.

“In some cases, it is healthcare workers getting sick and treating patients,” Nuzzo says. “In other cases, it is a patient going to a health facility for entirely different reasons and they end up sitting next to an [undiagnosed] Ebola patient. These might be places like smaller health clinics where people are bringing their kids for malaria treatment or something else.”

Efforts to ensure a steady flow of PPE and reinforce proper use have been mixed.

“Purchasing additional PPE doesn’t necessarily lead to systemic change in behaviors and practices,” Nuzzo says. “At one of the hospitals, they had given people a lot of masks, gloves, and gowns. But then people reported blood on the floor and they were wearing flip-flops. It’s not just necessarily about the equipment; it is also about training and education and safe practices beyond using gloves and gowns.”

Johns Hopkins is one of 10 designated Ebola treatment centers in the United States that have enhanced capabilities such as designated biocontainment units and other control and treatment measures. The 2014 outbreak in West Africa was characterized by a lot of confusion about PPE, particularly the finding that healthcare workers frequently contaminated themselves doffing the equipment. That may have been a factor in the case of two Dallas nurses who contracted Ebola but survived after caring for a dying patient from West Africa. The basic PPE needed is considerable in the new tiered system in the United States, even for frontline hospitals that will be looking to quickly hand off a patient to one of the Ebola assessment facilities.5


  1. World Health Organization. Ebola virus disease – Democratic Republic of the Congo. Disease outbreak news: Update Aug. 1, 2019. Available at: Accessed Aug. 9, 2019.
  2. World Health Organization. Ebola outbreak in the Democratic Republic of the Congo declared a Public Health Emergency of International Concern. July 17, 2019. Available at: Accessed Aug. 9, 2019.
  3. BBC. DR Congo Ebola outbreak declared global health emergency, July 17, 2019. Available at: Accessed Aug. 9, 2019.
  4. Henao-Restrepo AM, Longini IM, Egger M, et al. Efficacy and effectiveness of an rVSV-vectored vaccine expressing Ebola surface glycoprotein: Interim results from the Guinea ring vaccination cluster-randomised trial. Lancet 2015;386:857-866.
  5. Centers for Disease Control and Prevention. Interim guidance for preparing frontline healthcare facilities for patients under investigation (PUIs) for Ebola virus disease (EVD). Available at: Accessed Aug. 9, 2019.