The Ebola outbreak in the DRC continues to grow, with 39 new cases reported in the WHO’s latest Situation Report (4 December to 10 December). Most of these cases were reported in Katwa (12) and Butembo (8). It is now the second largest Ebola outbreak on record, with 515 total cases as of 12 December (467 confirmed, 48 probable), including 303 deaths. On Tuesday, the WHO’s Dr. Peter Salama tweeted that, while the first wave of the outbreak—centered in Mangina—has been largely controlled, a “second wave, more concerning [and] dispersed across many areas, has continued for over 2 months, with about 5 new cases per day.” This includes increasing numbers of cases and deaths in the Butembo and Katwa health districts. Of high concern is the potential for increased spread within Butembo, which has a population of more than one million people and is a major regional trading and transport hub.

The DRC Ministry of Health, along with hundreds of international experts from response and humanitarian aid organizations—including the WHO, Alliance for International Medical Action (ALIMA), MĂ©decins Sans Frontières (MSF), and UNICEF—are diligently working to stop this outbreak. For example, as of 5 December, more than 40,000 people have been vaccinated with an investigational Ebola vaccine, which Dr. Salama has credited as “having a major impact” on the outbreak. Other efforts include screening and decontamination of vehicles at points of entry, medical support, community awareness and mobilization sessions, and the implementation of various infection prevention and control measures to prevent transmission, among many others. Despite these dedicated efforts, the increasing number of cases suggests that additional strategies are needed, likely including additional human resources to conduct contact tracing. The WHO notes that in the past 21 days, more than 100 new cases (confirmed and probable) have been reported across 12 health zones. While contact tracing has been ongoing, challenges to such efforts have been reported, including security concerns and community resistance.

In a previous Outbreak Thursday post, we discussed the importance of prospective and retrospective contact tracing during the response. With prospective contact tracing, health officials quickly identify contacts of new Ebola cases and actively monitor them for any signs of disease, ensuring that they can be isolated if they develop symptoms of Ebola and prevent future transmission. Retrospective contact tracing aims to identify the source of transmission for a newly identified case to ensure all ongoing chains of transmission are known and monitored. Both types of contact tracing will be imperative for stopping this outbreak; however, contract tracing efforts to date have been incomplete. This hinders efforts to interrupt further transmission, including the use of vaccine, which requires having complete contacts lists in order to implement effective ring vaccination strategies. A number of experts, including from Outbreak Observatory, have highlighted the urgent need for increased resources to support response activities, in particular, the human resources needed to conduct contact tracing. These calls to action include high-profile commentaries in the New England Journal of Medicine and the Journal of the American Medical Association.

Each day, as new cases are reported, it is unclear how these cases fit into the context of current surveillance and containment efforts. Below, we pose some questions that might help us, along with others in the public health community who are not on the ground in DRC, better understand how contact tracing efforts are proceeding:

  • Was the newly identified case identified through prospective contact tracing and monitoring (ie, was he/she known to be at risk prior to developing symptoms)? If so, how closely was the individual monitored after being identified as a contact? If not, this indicates gaps in existing surveillance activities.

  • For newly identified cases, how much time transpired between symptom onset and subsequent isolation? Have all of the individual’s contacts been identified, and are they currently under monitoring?

  • For a newly identified case, was the individual offered the Ebola vaccine as post-exposure prophylaxis?

  • If a newly identified case was not under monitoring at the time of diagnosis, did retrospective contact tracing link the individual to a known case (ie, a known chain of transmission)? If not, this could indicate the existence of previously unknown chains of transmission and additional at-risk individuals or populations. This could also potentially indicate improved surveillance capacity that enables the identification of more new cases.

  • Was the newly identified case dead on arrival (ie, a “community death”)? This makes contact tracing difficult without the assistance of family or close friends who know the daily movements of the deceased individual, whether to identify the source of infection or potential contacts for monitoring and vaccination.

  • What is the estimated percentage of known contacts of Ebola cases that have been offered vaccine? What percentage of those offered vaccine received the vaccination? Are these individuals being adequately tracked to support clinical trials?

While the WHO DRC situation updates, DRC MOH updates, and other data sources are extremely useful in ascertaining the number and location of newly identified cases or understanding existing efforts to stop the outbreak, many of the questions posed above cannot be answered based on aggregate data alone. Rather, they require case-level (eg, line list) data to better understand the realities on the ground, particularly with respect to surveillance activities. It is likely that health organizations and other responders on the ground have this data, but without making this information available to the public, it is difficult to put Ebola case counts into perspective. The answers to these questions could provide useful insight into current contact tracing efforts and potentially provide evidence to further highlight the need for additional resources and strategies on the ground to ensure that all contacts are prospectively traced and monitored. This capability is critical to the rapid containment of new cases and, ultimately, to interrupt chains of transmission and bring an end to the outbreak.

The questions listed above are just some of those that the Outbreak Observatory team is reflecting upon as new cases are reported each day, but we welcome and encourage additional questions from Outbreak Observatory followers. To this end, we have started a Google Sheet as a repository for these questions. We hope this can serve as a resource, for us and for others following this situation, to improve how we collectively understand the outbreak and contextualize the published data.

Photo: Local clinical and sanitation staff and Médecins Sans Frontières responders at an Ebola treatment center in DRC during a 2012 outbreak.
Title: “Ebola in the Democratic Republic of Congo;” courtesy of CDC/Brian Bird, Ph.D. D.V.M.

Outbreak Observatory aims to collect information on challenges and solutions associated with outbreak response and share it broadly to allow others to learn from these experiences in order to improve global outbreak response capabilities.