We retrospectively examined ERRB responses during 2007‒2016. To compile the responses that occurred during 2007‒2014, we abstracted data from past branch activities databases and publications. To ensure the completeness of this dataset, we compared it with a previously compiled comprehensive database of all emergencies worldwide, including CEs and natural disasters, for the same period (A. Culver, Emory University, pers. comm., 2015 Aug 4). Sources of CEs included in this database were the Center for Research on the Epidemiology of Disasters Complex Emergency Database (http://cedat.be) and the United Nations Office for the Coordination of Humanitarian Affairs Central Emergency Response Fund archives of funded responses (http://www.unocha.org/cerf/cerf-worldwide/allocations-country/2006-2017-country). Included events were those that affected >10,000 persons and had a documented CMR of >1 death/10,000 persons/day. Sources for natural disasters were the Center for Research on the Epidemiology of Disasters international disaster database (http://www.emdat.be) and Central Emergency Response Fund archives; inclusion required that the event affected >10,000 persons. To compile emergency responses for 2015 and 2016, we abstracted data from branch administrative and travel records. Responses were selected to reflect >1 response/year and to include those in which branch staff had a major role.

Of 14 selected emergencies over the past 10 years, nearly two thirds were CEs; the rest were natural and human-made disasters (Technical Appendix Table). Responses were conducted in Africa, Asia, Latin America and the Caribbean, Europe, and the Middle East; activities included providing technical assistance or directly conducting assessments and investigations, implementing and evaluating surveillance systems, developing guidelines, providing trainings, and coordinating interventions. All responses featured extensive collaboration with a variety of partners, including the US government, UN agencies, governmental health entities, and both national and international nongovernmental organizations (NGOs). To illustrate the breadth and impact of the CDC and its partners’ work in humanitarian emergency responses, we highlight activities performed in 3 cases (Technical Appendix Table).

Reflecting on these 3 case studies and the other listed ERRB humanitarian emergency responses, several overarching lessons for effective public health humanitarian emergency response emerge. First, because humanitarian emergency response requires engaging in a broad range of public health work within resource-limited, fragile, or insecure environments, successful response requires developing close working relationships with other humanitarian response organizations. For CDC, these partnering organizations include national governments; ministries of health; US government agencies (especially the Agency for International Development’s Office of Foreign Disaster Assistance and the Department of State Bureau of Populations, Refugees, and Migration); UN agencies, including the World Health Organization, UNHCR, and UNICEF; and national and international NGOs. At a basic level, these close relationships allow ERRB and other humanitarian responders access to CE settings. These collaborations encourage standardization of approaches across the international humanitarian emergency response community (29) and improved coordination of response (6,18). The common use of these standardized practices has been facilitated by the dissemination of the epidemiologic approaches and methods championed by CDC during humanitarian emergency responses and through CDC-trained staff going on to senior positions at UN agencies. Finally, these collaborations permit ERRB and similar organizations to provide technical assistance while partners such as national ministries of health, UN agencies, and NGOs take the lead in implementation of interventions.

Second, because public health emergency responses often take place within the context of mass population displacement and fragile states, CDC and other responders must develop and apply epidemiologic methods and tools to be used in challenging and resource-limited settings. ERRB has contributed to several such tools. In the nutrition sector, ERRB enhanced the application of the emergency nutrition assessment software that facilitates survey planning, data collection, and analysis of anthropometric indices (http://smartmethodology.org/survey-planning-tools/smart-emergency-nutrition-assessment) and led the technical development of the Community-based Management of Acute Malnutrition report for monitoring programs to manage malnutrition in emergencies (41). In the communicable diseases sector, ERRB helped develop the evaluation tool for tuberculosis in resource-limited, refugee, and postconflict settings (https://www.cdc.gov/globalhealth/healthprotection/errb/researchandsurvey/tbtool.htm). In the sexual and gender-based violence sector, branch staff contributed to the guidelines for integrating gender-based violence interventions in humanitarian action (http://gbvguidelines.org/wp/wp-content/uploads/2015/09/2015-IASC-Gender-based-Violence-Guidelines_lo-res.pdf). Across these and other sectors, in settings where the evidence base for interventions is limited, CDC focuses on strengthening the accuracy of data to build a solid evidence base for interventions to guide humanitarian response, enhance global health security, and prevent morbidity and mortality.

Third, effective emergency responses must adapt to changing needs of emergency-affected populations. Humanitarian emergencies, especially CEs, which exacerbate the fragility of politically weak and unstable regions, could last several years without a clear endpoint. Although dramatically elevated mortality rates might decrease as a CE moves from an acute emergency to a postemergency phase, populations continue to be vulnerable to many of the same health risks. As the humanitarian response evolves and becomes better established, responders might need to strengthen disease surveillance, review and interpret public health data, and improve capacity of local or national public health systems. Responders must maintain a commitment to improving the function and resilience of public health systems within these fragile settings.

Fourth, ERRB’s work supports the work of CDC to prevent, detect, and respond to public health threats in fragile states under conditions that can result in regionally destabilizing effects and threaten global health security. Responding effectively requires that ERRB and other responders recognize 3 global patterns in population displacement: urbanization of the displaced, a shifting disease burden that includes noncommunicable diseases, and increasing security restrictions in areas of displacement. Understanding the unique aspects of urbanization of the displaced, moving away from the rural camp–based models of the past, suggests the need to change epidemiologic methods of surveillance and population assessment. In addition, because the displaced are increasingly likely to need assistance for noncommunicable, chronic diseases and access to long-term health services, compared with displaced populations in the past (9), the humanitarian emergency response community’s areas of expertise must expand to include this sector. Increasing security restrictions have sometimes prevented, and will likely continue to prevent, CDC staff and the humanitarian community from physically accessing certain displaced populations. Furthermore, CDC is the public health agency of the US government and not a humanitarian agency, and thus, ERRB’s responses are limited in ways that those of humanitarian agencies are not. These limitations include where, under what circumstances, and with which partners CDC staff can work. To address these limitations, ERRB staff is working to formalize remote support and program evaluation without sacrificing quality or comprehensiveness of assistance. More broadly, however, ERRB relies on humanitarian agencies to continue using epidemiologically sound public health approaches to guide evidence-based, effective interventions when CDC is precluded from responding.

Finally, ERRB responses show that response expertise is most useful when deployed early in an emergency and with a sustained presence. To that end, ERRB’s Global Rapid Response Team quickly matches needs in the field with expertise available from within ERRB and across the entire CDC, and these responders can provide longer-term support. In its first year of existence, the Global Rapid Response Team deployed >200 staff members to various emergency responses, including for Hurricane Matthew in Haiti in October 2016.

As the numbers affected by and intensity of humanitarian emergencies increase, ERRB and other response organizations must provide broader assistance. To that end, ERRB collaborates with partners; contributes to epidemiologic tools to be used in humanitarian emergencies; and, through the Global Rapid Response Team, responds more quickly and with more staff. The next steps for ERRB and other responders include improving capacity and resilience of public health systems in fragile states; understanding the public health implications of long-term, urban-based displacements; adding a focus on noncommunicable diseases; and providing remote epidemiologic support in a systematic way. In settings where ERRB staff, as representatives of a US government agency, cannot respond, CDC’s evidence-based interventions for emergencies are still implemented because of branch efforts in building local capacity for emergency response and training public health practitioners who then move on to work with humanitarian agencies. In these ways, ERRB continues to apply public health science to save lives in humanitarian settings while also working on the forefront of response-purposed detection and preparing a global health response workforce.