The CDC is stepping up efforts to fight Ebola in Africa, deploying more personnel and resources to stop an expanding yearlong outbreak in the Democratic Republic of Congo (DRC).

The World Health Organization (WHO) recently declared an international health emergency in the 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 were four cases in Goma, but the WHO vaccinated more than 1,300 contacts and had stopped transmission in the city as this report was filed.

“Right now, we have about 15 people on the ground in the DRC and in Goma responding to the outbreak,” Henry Walke, MD, MPH, director of the CDC Division of Preparedness and Emerging Infections, said at a recent press conference. “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 Aug. 18, 2,888 Ebola cases were reported, including 1,938 deaths for a morality rate of 67%. Cases continue to be reported among health workers, with the number infected rising to 153 (5% of all confirmed and probable cases).1 Of the healthcare workers infected, unverified reports indicate at least 40 have died of Ebola. No infections or deaths have been reported in deployed CDC personnel.

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.

“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 the DRC and the United States. 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 the DRC has made it difficult to contain the outbreak, which is spreading, even though an apparently effective experimental Ebola vaccine has been deployed. “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 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” strategy 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.

As previously reported, healthcare workers in the DRC are receiving the experimental Ebola vaccine, but the efficacy of immunization was unclear as this report was filed. The vaccine demonstrated high efficacy in one trial,2 but is now being used on an unprecedented scale.

The vaccine appears to be effective at preventing Ebola deaths, 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.”

The NIH is conducting a clinical trial3 to vaccinate adult volunteers, including deploying healthcare workers and other responders, against Ebola. The study sites include the NIH and Emory University.

Another established threat to healthcare workers is Middle East Respiratory Syndrome (MERS) coronavirus. Although it has not been sustained in other countries following introductions and outbreaks, MERS has established an endemic presence in the Kingdom of Saudi Arabia since it emerged in 2012, the WHO reported.4

As of June 30, there have been 2,449 laboratory-confirmed cases of MERS reported, with 84% in Saudi Arabia and the rest in 27 other countries, including the United States. There have been 845 MERS deaths, a mortality rate of 35%. MERS is a zoonotic virus that has established a reservoir in camels on the Arabian Peninsula.

“Limited, nonsustained human-to-human transmission mainly in healthcare settings continues to occur, primarily in Saudi Arabia,” the WHO reported. “The risk of exported cases to areas outside of the Middle East due to travel remains significant.”

While there has been community transmission, MERS is a particular threat to spread in healthcare settings.

“[T]ransmission in healthcare settings is believed to have occurred before adequate infection prevention and control procedures were applied and cases were isolated,” according to the WHO report. “Investigations at the time of the outbreaks indicate that aerosolizing procedures conducted in crowded emergency departments or medical wards with suboptimal infection prevention and control measures in place resulted in human-to-human transmission and environmental contamination.”

Since the last WHO update of June 30, 2018, 52 of the 97 secondary cases reported were associated with transmission in healthcare facilities. These cases included 23 healthcare workers. Patient infections occurred in those sharing rooms or wards with MERS patients, and some visitors also were infected.

“Although not unexpected, these transmission events continue to be deeply concerning, given that MERS is still a relatively rare disease about which medical personnel in healthcare facilities have low awareness,” the WHO concluded.

Globally, awareness of MERS is generally low and cases may be missed due to the nonspecific initial symptoms. “With improved compliance in infection prevention and control, namely adherence to the standard precautions at all times, human-to-human transmission in healthcare facilities can be reduced and possibly eliminated with additional use of transmission-based precautions,” the WHO noted.

A recently published analysis5 of a MERS cluster in a women’s dormitory in Riyadh, Saudi Arabia, confirmed that 19 infections occurred there in 2015. “Our study highlights the potential role of healthcare workers not responsible for direct patient care (e.g., hospital cleaners) in the spread of MERS,” the authors concluded. “Often, hospital cleaning staff may be from other countries, may speak several languages, and may be missed by efforts to increase infection prevention and control specific to MERS.”


  1. World Health Organization. Ebola virus disease — Democratic Republic of the Congo. Disease outbreak news: External Situation Report 55, Aug. 20, 2019. Available at: Accessed Sept. 4, 2019.
  2. 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.
  3. National Institutes of Health. Immunogenicity of recombinant vesicular stomatitis vaccine for Ebola-Zaire (rVSV[Delta]G-ZEBOV-GP) for pre-exposure prophylaxis (PREP) in people at potential occupational risk for Ebola virus exposure. Identifier: NCT02788227. Available at: Accessed Sept. 4, 2019.
  4. World Health Organization. MERS Global Summary and Assessment of Risk. July 2019. Available at: Accessed Sept. 4, 2019.
  5. Van Kerkhove MD, Aswad S, Assiri A, et al. Transmissibility of MERS-CoV infection in closed setting, Riyadh, Saudi Arabia, 2015. Emerg Infect Dis 2019;25. Available at: Accessed Sept. 4, 2019.